I dreamt about playing the guitar(I don’t play on the guitar) and I can’t stop do an air guitar! Why is that?
What do you mean exactly? That in the dream, you would want to be air guitaring all the time?
Besides, I took a guitar on my hands more times in a dream than in reality 
and played some original songs too.
I mean that I played the guitar in the dream and now IWL I do air guitar all the time. Why is that?
Maybe you like it? Try and explore your feelings about that, when you do it.
The dream improved my air guitar skills(lol if there’s something like that) and it feels different…
try a real guitar maybe you learned to play it in your dream
Maybe…lol