M.S.
I have a mild one, it's over my left eyelid, it comes and goes, I think it mostly happens when I have too much caffeine lol, very very mild, no one notices it but me, that's how mild it is, I saw so many drs about it and the best answer I got was this, sometimes the body just does something and there's no explanation for it, it does not happen all the time for me and and never affected my sight or any functions at all.