There are so many things it can be. My psychiatrist prescribed me Topamax in 2000 as a mood stabilizer but as a side effect it stopped twitches i had for my entire life. It was never diagnosed, even though it once happened right in front of this same dr and he asked me what it was! My whole body shook. I said, "thats my shiver, it happens sometimes." Google says it might be Jacksonian March, a mild epilepsy. If i try stopping the med, i get leg twitches at night.