I agree with Knott 100% and would like to add a bit. Becuase the tingling is fairly isolated it is likely related to imingement at the neck level (most likely between C6 and C7). It's more common to get a C5-C6 level impingement from slouching and based on what you've said this is not as likely to be an issue. What's interesting is that it comes on quickly when you raise your arm. This would lead me to think that there is some sort of biomechanical issue that is contributing to the problem, such as excessive movement at C6-7 compensating for something in you upper back is not moving well. The other possibility is that your getting nerve pressure in your neck area from excessive tightness of some of the muscles of your neck (the scalenes in particular). Either way, it needs to be looked at by a PT or similar, (I'm not a big fan of Chiropractic but I will often recommend a Doctor of Osteopathy, DO for short).

Good luck with it all. And don't leave it too long before you get it checked!