I Periodically Have A Pain In My Left Calf, Mainly

I periodically have a pain in my left calf, mainly experienced as unbearable pressure. I have to jog or walk, move it immediately. It comes at odd times, e.g., in bed middle of the night, sitting down, driving. Probably happens 4-6 times a year. I can't see any swelling, discoloration, heat... just feels like my leg will explode.