When i hold my teeth slightly apart, like millimeters, my lower jaw very finely "tremors" causing my teeth to come into contact with each other, almost like a chatter. only happens in this specific scenario, and i have no other symptoms. concerning?

I wouldn't be concerned about this type of tremor unless you note intention type tremors of your hands or head or if you have a family history of essential tremor. When we tense a muscle group in an unusual posture it's not unusual to have transient tremor of the muscle used & I think this is what's happening with your mouth. A neurologist can evaluate & advise you if you still have concerns