I have noticed from a month that my shoulder muscles vibrate like a vibrating machine. This is sometimes difficult to understand . It gets triggered any time. And its not a small part that does the twitching but rather a big shoulder muscle. It happens nearly 5 times a day. History : i have a shoulder injury because of lifting the weights in the gym incorrectly about 8 years back. I also have shoulder pain once in 2 years. I have consulted a physiotherapist and he told me that the injury has caused a very small injury in the shoulder muscles for which i dont have to worry about. What do i do ?