My husband has the shakes during sleeep--the kind you refered to as hard sudden jerks I believe. This happens during nap time too. I asked his ND and she said it was caused by the parkinson, I didn't ask her why. He does not have the tremors (day time) since early on after going on medication. The other people in our support gp always ask 'how come you don't shake?' Mary CG for Mel 76/12