What Causes The Thumb To Shake?

I have a white blood cell condition, and I have random issues a lot, but last night my thumb started uncontrollably shaking. My body felt off and jittery, but my heart beat doesn't seem to be beating fast...it actually seems a little slow. I get occasional vibration down my thumb. And I don't think it is coming from typing or texting because my whole body begins feeling weird at times.