if you have no other symptoms and this is recurring, accompanied by numbness in one or more fingers, especially after typing, writing, or driving, or if you have pain in your wrist, I would suggest carpel tunnel syndrome. This is correctable by a very common surgery and often affects people who are frequent typists or writers. HOWEVER, as stated by Tsalyer, if you have ANY other symptoms as they described, you should see someone immediately as it could be an indicator of heart complications that may be emergent.
If your left arm and hand are tingling you and it is accompanied by pain, shortness of breath, or the feeling of chest constriction you should see a doctor immediately. Do not wait go to the emergency room. If it is not you still might want to consider speaking to a doctor.
Could be a pinched nerve (not serious), but if, as Tsalyer noted, you have any shortness of breath, tightness in chest, it could be problem with your heart (serious), and you should get to ER right away.