I don't grind my teeth, but some times my teeth chatter (like i'm freezing cold) so hard that you would think that they would all crack and fall out of my mouth.
Sometimes, when I realize this is happening I usually put my shirt sleeve or an edge of a blanket in my mouth so I don't hurt my teeth.
The chattering last sometimes for 15 to 20 minutes. My bottom jaw usually is sore when its done.