I have noticed over the past year that when I am lying down or sitting back in. my recliner I will suddenly "jerk" (not to be confused with the 60's dance). It never seems to occur when I am just sitting in normal position. Sometimes I feel as if I am going to jerk right out of my bed. It seems to occur most often when I am in a state of near-dozing. I have not mentioned to any doctor because I have not encountered any here locally who seem to be interested in delving into such matters. Have you been to see a neurologist? Seems like that might be a good start. I wish you well.