Did God create the universe or did it just occur naturally?

Technically, it would be the same thing:

If one believes that a God created all things, that would include nature, all processes that are natural and the results of those processes. God is, by association then, the initiation of nature.

Belief is a personal choice; it doesn't require evidence, nor does it authenticate any claims.

I tend to lean toward where The Evidence leads us, the realm of science, but I understand that we may never really know the full facts of this matter... and, so what? I assert that "How It All Began" is of little importance compared to the greater significance of us being here now. 

The Bible simply states: “In the beginning God created the heavens and the earth.” (Genesis 1:1) Without God’s eternal renewing power, the universe—including the solar system that we depend on for stability, light, and energy—would descend into total disorder and ultimate destruction. Thus, if left to itself, our earth would “wear out,” or come to a permanent end.

Even better, God created the universe to occur naturally just like how he created evolution to do the creation job for him

"Of course every house is constructed by someone, but the one who constructed a things is God." Hebrews 3:4

I'm a firm believer in the Big Bang Theory. I just can't wrap my head around some big deity hanging out in Nowhereland and then deciding to create this big dark expanse and fill it with stars, planets and ONLY putting humans on one planet. I'm sure that if life were on other planets, this deity would have bragged about it in The Big Book.

I answered this question in some detail on Ask. I'll just copy my answer here.

ALL things come from God. ALL of science is based on what scientists
have discovered about his Divine essence. The cataclysmic and holy
explosion that we euphemistically call the Big Bang was merely a
rapid expulsion of Divine Methane.

From Didge’s Gospel we learn:
1:1 In the beginning before all things were created, was a Being who inhabited the All-There-Is; and his name was Aye, for he was One.
1:2 Aye was an Epicurean, nay, he was THE Epicurean, and his larder was a cornucopia of culinary delights.
1:3 And Aye feasted.
1:4 Without pausing for sleep or rest he ate continuously for six days and six nights, and then he was filled.
1:5 And on the evening of the sixth day he was no longer able to retain
all that he had consumed and a mighty explosion occurred.
1:6 The stars were born, and the planets, and all that there is, and they
sped from him at enormous speeds, forming constellations in the
firmament.
1:7 And Aye collapsed in intoxicated slumber and lo, it was the seventh day.

So you see, science and religion are wholly compatible.

My theory is that he/she made the Big Bang happen, but then again I'm not sure he/she exists.

I believe that the Big Bang occurred naturally, but it is possible that a deity did create it.

Science can offer no solid answers in respects to how EXACTLY the universe came about. We can determine WHEN it started (again not exactly but around 14 billion years ago), and hypothesize how the planets were formed, but we have no absolute working models to establish any Scientific theory. We can tell from other natural occurrences what most LIKELY might have happened.

If we want to assign a deity to the universes creation, then which do we pick and what makes this a more valid choice then random occurrence? There are many creation stories from ancient civilizations, each assigned to a different God or Gods. Is this more likely how man assigned the "Unknown" in the shadow of primitive ignorance? While speculation has it's place we find it more grand and magical the further back we go in our past. The scientific method and our technology allow us start each question we have about our natural surrounding with a less primitive ignorance, thus providing a more suitable answer other then one based in Supernatural belief . . . This is the path to knowledge.

While it is easy to try and establish "Intent" with the end result, one must understand that where we are NOW could literally be so different based on any change to occurrences in our past. If we remained sentient cognitive beings but now with one eye and scales breathing carbon dioxide and giving off oxygen, would we not try and assign a possible deity to have created us in their image, and how wonderful the intent of this creation that gave us the perfect planet suitable to our life? Would we not find beauty in whatever environment we lived in and attribute it to some Supernatural "Watchmaker" saying it could only happen by design?

The point is, we may never know, and we SHOULD be okay with that. For me, it is better to assign "not Knowing". There is no need to be inserting a magical place holder from our primitive ignorant past.

In the beginning God created the heavens and the earth. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.

And God said, “Let there be light,”

Sound is a formation of energy, light is another. Everything is made of energy vibrating at a certain level.

E= mc 2 - Mass is a three-dimensional form of energy.

If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.” ~ Nikola Tesla

This is why in the bible you are not defiled by what you put in your mouth but by what comes out of it. Matt 15:11

Proverbs 18:22 Death and life are in the power of the tongue, and those who love it will eat its fruits.

Matt 12:37 For by your words you will be justified, and by your words you will be condemned.

Proverbs 13:3 Whoever guards his mouth preserves his life; he who opens wide his lips comes to ruin.

Luke 6:45 A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart. For the mouth speaks what the heart is full of.

Eph 4:29 Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.

Proverbs 15:4 The soothing tongue is a tree of life,
but a perverse tongue crushes the spirit.

1 Peter 3:9 Do not repay evil with evil or insult with insult. On the contrary, repay evil with blessing, because to this you were called so that you may inherit a blessing.

Matt 12:36 But I tell you that everyone will have to give account on the day of judgment for every empty word they have spoken.

he created it.

First off, if one wants to say it was God that created everything we first have to determine which God. Each religion states that their God created it, so perhaps we should just take a vote. The biblical God didn't, he only created, according to the bible itself, dry land and a dome over the earth, so he's out. I go with Brahman.... Wait maybe the earth was terraformed by aliens? Yeah, yeah, that's it.

Believe what you want, but the only evidence there is, says the BB is how things came to be and that was discovered by... Hold on,.. Wait for it,.. A Christian Priest. How the BB happened, is up to you, as we don't know how it happened... As yet. We only know it did, nearly 14 billion years ago. Humans and their Gods are but a speck on the history of the universe.

Before answering this questiob we should all now that the answers we give here are merely opinions and not more since we are bo experts in the field.

I was raised as a Muslim and naturally muslims believe God created everything. But the thing is I do not buy it. I am an atheist now and I do not believe in God. It seems illogical that an entity (God) started up a gang (a bunch if angels) and orderd them to start up a univers. I do not simply buy it. I believe the universe is the result of the big bang and the big bang has nothing to do with god. As Steven Hawking says: The universe started from nothing. So no God did not create the universe. The Universe has been created from nothing. It was just an incident which created the universe.