Notice any patterns with them? There are a bunch of different types of twitches. Ah the many subtle joys of AF.
Dystonias are a large grouping of them. If you get them when falling asleep it's Myoclonus. That's the waking up with a jerk while falling asleep.
Lots of research and comments out there on twitches, but I couldn't find much info on my varietal. I still get somewhat dramatic twitches, mostly in the torso, and it happens when I'm changing into relax mode. Commonly when going to sleep back in when things were bad, now just when I'm going from work mode to non-work mode.
Magnesium helps to relax, but it never seems to truly go away.