Hi,
Numbness in the arm can be due to neuropathy or impingement of a blood vessel. Try a different sleep position and avoid taking tea for sometime and see if that helps, if it persists please get yourself evaluated by a physician.Also elevating your arms at night and deep hug exercise helps in maintaining blood circulation in the arms.
Hi, it seems you are having pressure effects on nerves or blood vessels may be dure to faulty posture you take, try changing your way of sleeping position it may help you otherwise you can consult a neurophysician who can examine you.