Usually when a loved one comes to you, they are just stopping by to say hello, and to let you know that they are well and happy, not suffering, and are watching you through your life. These should always be happy dreams, if they aren't and you like get a feeling that they might be trying to warn you, then you should listen, usually there aren't any other types of dreams about them coming to visit. Hope this helps.
My grandfather passed away 3 yrs ago. I find that I dream of him often when I'm going through a personal hell. Maybe this is because he was always such a great comfort to me when he was alive. Perhaps it's my minds way of self-comforting now that he's gone. Or maybe it's just that I really miss him.
Most dreams need to be contemplated by the dreamer to have meaning. When I dreamed about my dead Grandmother (she died at the end of March 1992 then I dreamed of her the first week of November 1995)... It seemed to be that she had been searching for me and finally found me to let me know she was fine and for me to know everything would be alright. Without knowing the content of your dream about your grandfather or you... It is safe to say only you can say what the dream meant &/or why you had it--
My dead grandfather was telling me not to go back to sleep
Maybe you just miss him
It could mean that you have inherited something from them such as a blessing or a curse