Oh wow. I'm so glad that someone posted this. I get this sensation like vibrating especially in my shoulders at night when I am trying to go to sleep. If it gets too bad I have to take a flexeril; which then ruins my morning because I am so groggy.... I didn't know why this happens but apparently from the other posts this may be common, hmmm very interesting.
It is so weird because you can not really see the spasm but it is there!!! Hope we don't all shake off our beds. HAHA