What Causes Severe And Repetitive Thigh Pains?

I had sudden severe thigh pains, late a night(sudden onset). The rt posterior thigh(lasted 4-6min.). 4 hours later, the left posterior thigh, same area as right. I have no diseases except ulcerative colitis. I haven t done any physical exertion and these cramps occurred while I was laying on my back in bed. The first caused so much pain and paralysis, I flipped to my rt side until it subsided. At 1am the second one occurred on the lt thigh and I was awakened from a deep sleep when this happenned. I flipped to my left side, same duration of time(4-6 min). Never felt or heard of anything like this.