lower back discomfort after 5-7 hours sleep

Hi

I'm healthy, just turned 40, no history of trauma and stretch every morning. Recently after 5-7 hours sleep, my lower back starts feeling like a nerve is pinching and have to get up and walk around. During the course of day gets better and comes back again at night during sleep. Could this be caused by an old mattress? Any suggestions for a new one or what to do? Trying to avoid meds as much as possible.

Thanks