Extreme leg muscle pain .

I need opinions from people that waitress/carhop or are on their feet everyday.

So I've carhopped at sonic 40+ hours, 6 days a week for 3 years now. But everyday after I get off work, the muscles in my legs tighten and will cramp for hours. I'm left constantly stretching my legs out that night. I've tried warm/cold baths to relax but that makes it worse because of the contrast in temperature after I get out. It seems rubbing in lotion and stretching them are the only ways I can get relief. I've considered dehydration as a cause, but I often drink at least a liter of water a day.

Any tips or reasons for this?