Well, the last time I had my body jerk awake was a few nights ago, and I don't remember seeing or hearing things, but instead it seemed like just before I jerked, I was simply thinking thoughts in my mind while in very light sleep. The thoughts seemed completely automatic, as if my mind were thinking for me. But I couldn't remember the thoughts at all (even thought it was only seconds ago I was having them), though I had a sense that they were very interesting (but not scary). I guess I can't totally rule out the possibility of something else occurring, such as hypnagogic imagery, since I'm not remembering much.

This actually happened very often during the last few nights when I woke up after being asleep for a few minutes. I never remembered the thoughts, just knew that they were there.