Not really a "gifted" question, but do any of your kids do this (have done this in the past)? My DS6 hums, clears his throat, occasionally has rapid eye blinking, and otherwise makes some funny noises. It comes and goes- we used to notice the humming as a build up to a tantrum/freakout when he was in preschool.
Seemed like he had gotten over the noise making and eye blinking, but as of the last few weeks it's back full force. I can't figure out the trigger (maybe hidden anxiety that he's not discussing?). No other "stim" behavior, and as far as we're aware, no autism, ADHD, etc. I'm not necessarily worried, except that I wonder if he has some sensory issues that we need to address or if this is a sign of anxiety?