I get the internal tremors too although they're not as bad as they used to be. They seem to be worse when I eat too much sugar or when I get anxious or stressed. I was told by my cranial osteopath that the mercury was in my nervous system and that was causing the tremors. It's not a nice feeling and makes it really hard to relax.
I also get flu like syptoms on and off which I've had since I was a child and never knew what caused them.