I just had something very worrisome happen. I was laying down reading a book and I was slighly leaning more on my right side. All of a sudden, my right shoulder all the way down to my right elbow started shaking or quivering very badly. I changed position and it stopped. I then rolled back into the same position that I was in and it started shaking badly again. Has anyone else every experienced anything like this? It really scares me. It's not even like I was exercising those muscles.