[dmuth]

Not a doctor, but I have/had similar problems, and saw a number of doctors and specialists about this.

Whatever it was, it wasn't understood by medical science, but the best thing we were able to pin it down to was "muscle spasms". Over time, I found that seeing a myofascial specialist, yoga, and physical therapy (read: Apple Fitness Plus) helped.

If you'd like to chat more about this topic or just pick my brain, my email is my username AT my username DOT org.