I've never really noticed internal tremors so much, or maybe just forgot if I had them! But quite often I find my hands in a slight tremor, and once in a while, my head will slightly shake.
Myself 09 mentioned it feels like a minor electric current, which reminded me...since you were diagnosed with fibro, have you found that a static electricity type of shock seems (almost overly) strong?
I use metal bowls at times when I'm cooking at the stove, and if I happen to touch one of them and something else like a pan at the same time, I can get some incredibly strong electric shocks. I don't recall that ever happening before fibro hit me. It's almost like the electricity "jumps."