I get eye twitches and really bad tricep twitches, sometimes delts, for me it's always low magnesium, plus stress and muscle tension. You take magnesium I'd guess it has to be stress causing it. You say you aren't stressed but are you sure? Us as dudes have a way of thinking we can handle more then we actually can, sometimes stress sneaks up on me and I won't even notice until my wife catches it and asks why I'm blowing up on people. For me to notice that I'm stressed out I have to be almost at a 10 out of 10 on the scale.