Mine gets worse whenever I'm not up and about, walking or running. The morning is the worst. I drive about 5 hours regularly - just the last few months my feet and legs have been getting numb and painful after about an hour so I make a pit stop, hobble around until the stiffness is gone, then get back on the road. I don't know why, I just know that it does. My neurologist said that it's Restless Leg Syndrome which quite a few of us seem to have.