I have felt that way when my anxiety was at its worst. I think its adrenaline. I would wake up and feel like I was vibrating. It got so bad that even my husband could feel it in bed. I am now taking Prozac 10 mg in the am and xanax .25 mg in the evening and it does not happen anymore. I normally am against taking meds, but it got so bad after 2 years that I finally gave in and am so glad I did. I am feeling sooooo much better!