Why is my teeth chattering in my sleep?

Possibly grinding.: Some people grind their teeth when they sleep. This can sometimes happen if there is a discrepancy between where your teeth fit together, and where your jaw muscles feel comfortable. I suggest you see your dentist. If you are grinding, you may benefit from some kind of night guard.

Bruxism: Grinding cused by a bite problem, stress or sleep apnea. See a dentist about this so you don't damage, break or wear your teeth.