My body shivers and shakes continuously for quite some time when i am trying to sleep. And i am unable to control it. And it has happened twice so far in last month. During day time i dont have any issue at work. I got my full body checkup done last week and all reports are normal. Don't have cold or fever or anything. What could be the underlying cause ? Please suggest what needs to be done. I am bit worried about the same. I was tested covid +ve 2 months back and recovered well with no issues.