My cat had twitches, and was really nervous all the time, we took him to the vet, got him some blood tests, and it came back a thyroid problem. First we got pills for his food, but he didn't like to eat it, so then we told the doctor and he gave us a pen that had a cream that we swipe in his ear twice a day, which seems to be working. Hyperthyroidism was what my cat had, I think it is similar in dogs too.