Is 16 too young for int. claudication the symptoms fit? pain in the legs when walking even short distances almost like cramping but goes with rest?

Not realy: Intermittent claudication in a young patient is unusual and should prompt a search for causes other than atherosclerosis. Osteochondroma popliteal artery entrapmentsyndrome cystic adventitial disease fibromuscular dysplasia, takayasu's arteritis buerger's disease, or thomboangiitis obliterans.

Possible: There may other sources other plaque, possibly congenital issues.