Excellent advice, John. Once the doctor has ruled out serious problems like a "transient ischemic attack" (temporary diminished blood supply to part of the motor center in the brain, which sounds like it's very UNlikely in this situation) or a generalized circulatory problem, you might consider seeing a physical medicine specialist (a/k/a PM&R physician or physiatrist--this is an MD, and not to be confused with a physical therapist or physiotherapist) or an occupational therapist who works with musicians. Could be this is the result of time-related changes in the areas the nerve goes through, as suggested above. In which case, specific therapy or altering your playing position would probably help.

Aloha,
Mark