Has this ever happened to you? You're drifting off to sleep, and then all of a sudden feels like you're on a roller coaster ride, you feel like you're spinning around and swooping all over the place, until finally you fall asleep. It sure does happen to me alot.
Then theres also nights when I fall asleep, and it feels like I'm falling out of bed, I wake up and brace myself for the fall but find that I didn't move at all...
I'm not complaining though, it's sort of fun

but does anyone know what causes it?