I agree with mellors.....sometimes our nasal passages are clogged and need a bit of help. Thrashing could come from the not breathing part. It could also be a sign of sleep apnea, and you should indeed have it checked out by a doctor. They can also tell you if you are having issues with polyps that grow inside the nasal cavetey and hinder breathing also. Could be a number of different things.

Wishing you luck!

Hugsss
sabby