Ill get a heavy feeling in my upper left leg. only occurs at rest. i can walk/run miles with no issues. comes for about a week then gone about a week?

Heavy in LU leg: May be piriformis syndrome which is compression of sciatic nerve by piriformis muscle in the buttocks. Relieved by walking stretching . May be GI constipation, with radiation to leg from pressure. May be intermittent hernia . Would check xray of left leg r/o lesion and assess if could be constipation or hernia or pirifirmins syndrome f/u w/ doc.