Yes have experienced it, nope don't think it's anxiety either. This was one of my first symptoms, except in the heydey of my onset, it would follow a night of horror - internal tremor/trembling, or electrical buzz, however it is experienced, muscle cramping, tingling, and massive cold sweats. In the middle of the night. Everyone else asleep. And me certain I had a degenerative neurological disease onset.
People who haven't experienced the tremor/buzz don't understand when you try to explain it and physicians will try to name it by calling it anxiety. What they want to tell us, I believe, is "whatever it is, you are going to be ok, just try to relax" I am quite experienced at experiencing and treating anxiety and this is not it. It is part of this large bag of symptoms. Gabapentin/neurontin has helped me with this partic symptom, and just a small amount (200 mg tid or 300 mg bid)