Depending on the age of the dog, it could be the onset of arthritis. I have a cat that is only 2, and she has it, I would suggest that you have her checked out, I don't think you want to make her suffer. Good luck to you, hope this helps.
My Dog's Legs Jerk At Night And She Limps In The Morning. She Is Still Playful But Tosses And Turns At Night. What Else Could This Be Besides Arthritis? Please Help Me. Is Glucosamine Any Good For Her?
It could be restless leg syndrome. it can happen in dogs too