Have no idea, so only advice is to stay off the internet. It's only useful after you have a diagnosis, not trolling for symptoms. If you haven't been exercising regularly, it could just be the body getting used to circulation where there hasn't been much. If it's true you're just starting up an exercise program where you were sedentary, especially for a smoker, build up more slowly than you would otherwise.
I have experienced similar symptoms and mine were linked to anxiety and an underlying heart condition. I feel that you should be evaluated by a doctor at your next possible convenience, however, as some of those symptoms are potentially for a more serious condition which needs to be ruled out.