Teeth chattering - Miniature Schnauzer

Question
Cassie is 13 years old and has been in excellent health all her life.  Only last nite I noticed the teeth chattering - this is not continuous but happened a dozen or so times through the evening and again this morning - for only a couple of seconds at a time.  She is now napping and is fine.  What is this new phenomenon?

Answer
I wonder if she doesn't have a loose tooth in there that is bugging her and her "chattering" is trying to get it back in place so that she can close her mouth properly. Open that mouth up and take a close look and poke at all her teeth. She may need to have a tooth pulled.