i've never had the constant shaking, but i do tend to get very anxious, more anxious in a given situation than a normal person would, it is sometimes accompanied by shaking but not normally. Usually just more panic attack like symptoms (increased heart rate, slight difficulty breathing, some times chest tightening, normal panic symptoms).

I would say try the doctor, but don't get your hopes up. The human body is such a weird, wonderful thing that it stumps doctors a lot more often than people would think (or at least this has ALWAYS been the case with me.. go to the dr for x ailment, never get a diagnosis, treatment or anything. just general things to do.. *sigh* ). Good luck with your testing though, i hope they can figure it out.