What kind of Dr. should you see for left arm numb and tingling?

There are few reasons but first I should say that what you describe falls among the indicators of a cardiovascular incident -- a heart attack. If you also experience pain in your chest, sweating, difficulty breathing, turning pale, or if this injury alone makes you worry, consider a 911 call. If you rule out heart attack, these symptoms are also indicative of a back injury, typically in the cervical or thoracic back. If you've had a recent back injury (including any deceleration event that could cause whiplash), this may be the answer. If so, a course of ibuprofin or aspirin might help. I'd also cold pack the back if you can find tender spots, and see if this goes away in an hour or so. In any case, if this problem continues, your doctor needs to know.