Is there any medical reason for not being able to move after waking from a long way?

Sounds like DOMS: A variant of delayed onset muscle soreness. If the walking was unusual or vigorous to you, like a new exercise, the response can be normal. While exerting your muscles, there is some microscopic tearing, and an inflammatory response to repair these tears. This is what makes you stronger. But if your exertion is suddenly great, you may get overwhelmed by the inflammatory response. Rest & ice.