Hi Momteach and Welcome-
I too had an MRI and numerous tests done and all came back normal. My feet and hands/arms go numb easily on me. Have to get off my feet when that happens and rest my hands and arms also till the feeling comes back.
I also get that internal trembling feeling. Did not have any of these symptoms prior to fibro, so I think it is just symptoms of it. It is the goofiest stuff! It's like our bodies just do whatever they want.