My money is on peripheral nerve injury from foraminal stenosis/impingment of nerve root; you'll want to steer away from activity that compresses your cervical spine or extends your neck i.e. upright rows, lat pulldowns behind the neck, lateral flys, military press etc and conversely do things that relax your neck, upper traps, scalenes SCMs and that gently stretch your neck like massage, suboccipital release, light cervical traction; any activity that increases neurologic symptoms, though, should be avoided.