What Causes Cold Sensation In The Legs?

I am experiencing a coolness in my legs and feet intermittently. Oddly enough, it quite often occurs a short time before or after a bowel movement. Not always but very often. I am wondering if those nerves involved with the lower body are also involved with the colon. Often it occurs when I have been sitting for a while working on a project and it makes me wonder if there is a position I am sitting in that pinches a nerve that triggers the result in the legs, and maybe stimulates a bowel movement. This has been going on since about mid-Feb.