I feel it from the inside, too! I thought it was really weird, but I've noticed that it tends to precede the visible tremoring...as in, I can almost tell when my hands and legs are going to start shaking because I get this feeling. I'm pretty sure I'm the only one who knows anything is going on, because I asked someone if it looked like I was shaking when I felt this one time (I felt like I was going crazy!!!) and they said they didn't notice anything.
It goes away after awhile, but the shaking in my hands and legs (I notice it when I cross my legs and the top leg is slowly twitching back and forth) sticks around for a lot longer.
Same with me inner trembling, mostly upper body.
I get inner trembling...at least i did until i started Armour. It has since then gotten a lot better, not as frequent. Mine was all upper body.