Fletcher does what you are describing, and it drives me crazy! He has been to his vet numerous times, and last year I took him to a specialist. We still don't have a real answer He does have pretty bad arthritis, so it could be pain, but like you said, why all of a sudden, when just lying there asleep He also has allergies, and is very sensitive to the heat, could be that I wish I had an answer for you, and maybe your vet will be able to pin down a cause for your girl, but at least you are not alone