I’ve found it to be the opposite; if I don’t move enough for long enough, I get stiff and sore and any existing injuries feel worse. I think it’s at least partly due to my job, as it requires sitting for longer than a human being should.

Having done manual labor before changing careers, my experience aligns with what others have already said: hydration and stretching are your friends. To add to that, I found supplementing with creatine and BCAAs to be helpful when I was a package handler. Creatine is ridiculously expensive now, but might be worth the price if it makes you feel better.

ETA: hydration matters not just during your shifts, but also before and after work. If you don’t do this already, try drinking a few glasses of water before bed and see if it makes a difference in how you feel in the mornings. I tried it for a few days and it made waking up less painful, so I try to make sure I’m well-hydrated before bed.