Has this just recently started? Do you sleep on your back? Usually numbness and tingling us from a circulation restriction which can certainly happen if you're lying on your back. Try sleeping on your side with a pillow between your knees. If back sleeping us the only way for you, try to elevate your shoulders and back a well as your knees to keep from cutting off the blood to your leg.
Other than those things, I'd probably tell my doctor about it.