Stress, anxiety can be the underlying cause for your symptoms. Your heart and its condition is very good, but that wouldn't rule out arrhythmia (abnormal heartbeat, etc.). For peace of mind, you may want to get a health evaluation.
My thing is - I have an office job. It's a very easy job, but it's a very quiet, slow, boring job, and sometimes I fall asleep, still sitting in my chair. When I wake up again, my whole body shakes, and sometimes I wonder if it's a small earthquke, because it's the same vibrating feeling. It goes away after a few moments, but I'm wondering... maybe it's adrenaline? Because I know I shouldn't be sleeping at work (it's not like I do it on purpose) so when I hear something or realize I'm sleeping, I snap back awake, and that's when I feel like I'm vibrating.