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Well, it certainly could be related to the way you're sleeping - from a neurologic point of view, it is possible that the sensations you're experiencing could be related to the nerves in you're arm. Carpal Tunnel Syndrome, which is due to a compression of a nerve (the Median Nerve) at the wrist. It frequently causes pain and numbness in the hand / fingers but can present in a variety of ways and is typically worse (and initially presenting) at night. Another possibility could be compression of the Ulnar Nerve at the elbow. From your history, it's difficult to assure this is a neurologic problem - but these could be possibilities. A good neurologic evaluation and, importantly, an EMG (an electrical study of nerves and muscles) can assess these possibilities.