Nerve problems in neck. Recently I was riding my motorcycle and my (R) arm started shaking uncontrollably. Tingling in hand/leg also. Hypothesis?

Nerve. You might possess cervical stenosis, associated with nerve pinching on the right side, but the uncontrollable shaking could represent focal seizure activity. Alternatively, the tingling could be due to peripheral nerve issues. A neurologist could sort all of these challenges out.
Need MRI. If you have neck pain with nerve symptoms, you need an urgent MRI and doctor follow up. All the best.
See your doctor. You need a neurological work up to determine the cause of your symptoms. Don't ride your bike until medically cleared by your doctor.
See a neurologist. hand shaking is not normal specially if affect one side only,that mean something wrong in the brain, you need to see a neurologist. good luck.