The electrical shock you describe is pretty ordinary -- it's a nerve in your arm that has been irritated by you rubbing it (or perhaps having been leaning on it). Do you remember the pain you experience when you hit your "funny bone" -- the bone in your elbow that will send that sort of shock through your arm? That's what's going on here -- rubbing the arm "wrong", hitting that nerve agains a bone (you'll notice how near to the surface your bones are there, in your elbow..and the nerves, too) and causing the "shock" sensation. Probably nothing to do with MS..
and nothing to do with L'Hermittes, which DOES have something to do with MS, but is a shock sensation that usually starts in the neck, and moves down through the shoulder, sometimes down the back, through the butt, and down a leg, depending on it's severity.