Okey dokey. Don't despair or go looking for a cemetary plot.Doesn't sound that serious. It is very likely your problem involves an injured, stretched or pinched nerve in the cervical vertebrae. There are Seven of these critters and eight nerves waiting to cause trouble. There is also a lesser possibiloity of a blood vessel that is pinched. But I would go first with the cervical etiology. Apply axial traction while you are having the symptoms,and if the symptoms immediately disappear, you have a pinched nerve in the cervical area! Easily treated with an axial traction device, anti-inflammatories, range of motion exercises, and perhaps a few valium.
I've a similar problem. But mine is caused by the overuse of my shoulder in playing the overhead shots in badminton. Somehow I don't have rotator cuffs problems but the tightness of my arm muscle (especially armpit) is so severe that it impinged my nerve an I get some muscle twitching and pain. I was told to take up swimming so as to tone my whole body muscle. I am trying to do the freestyle (or backstroke) by reaching as far as I can with each stroke.....and this is stretching my armpit and also strengthening my entire arm (including the armpit). It also helps to tone my back muscle at the same time. Give it a shot. If you can't swim, try exercising in the pool using movements that's for the arm and back muscle. Do it consistently when you start, but it's not a lifetime thing since your muscle will get into shape and tone up. Then you can reduce or even stop the exercise if you want. It helped me a hell of a lot.
I had this same problem but solved mine ....bought a carpal tunnel brace seems to be fine now...I have no insurance laid off so cant afford doctor tests....good luck and hope this helps anyone else with this problem