my wife drives a 2008 Kia Sedonna, the brakes are making a grinding sound but ony when she leaves work for lunch, the van stops making the sound after about 3 stops, it does this every day, The van is sitting in the parking lot for about 4 hours before she leaves for lunch. I rotated the tires and everything looked fine, the van only has 12k on it? What the heck could it be?