Hello Scoots86: I don't know if what you're experiencing is similar to a myoclonic jerk. I experience these. Just as I'm falling asleep my whole body jerks... seemingly quite violently sometimes. Sometimes, as it occurs, I'll dream I'm falling. In my case, most times it doesn't seem to affect my sleep. Occasionally, however, I'll then have difficulty getting back to sleep.

As I understand it, in most cases, myoclonic jerks are harmless. Occasionally, I guess, they can be an indicator of a more serious condition. Since you had that car accident, it may be worth checking back with your doctor. I'm not aware of any exercises one can do to prevent these from occurring. From what I've read doctors aren't even sure why it is these happen.