What Causes Radiating Pain From Buttocks To Leg?

Hello. I was wondering if you could help me diagnose something. I ve been getting shooting pain running down from the top of my right buttock to my upper right leg. It comes and goes and sometimes lasts days and seems to get worse when I shift my weight until I warm up from something like stretching which makes it stop for a while. When it gets bad it feels like it s radiating up and down in the same area and can even make my leg almost lock up. I m a 30 year old male otherwise healthy although I do smoke and drink lots of coffee. Thanks for your time!