It could be (frozen)condensation on the brakes. I like to pump the brakes when I first start out in the morning. That usually clears out anything that might have frozen on the rotors at night. I am not a scientist, but I think that the rotors pull the moisture at night to cool off when you stop and tur off the car. Someone might have a better answer as to why it happens. I really don't have a problem in the morning. I do hear a slight grinding noise in the morning when I brake and I account that to condensation and slight rust on the rotors. Try pumping the brakes when you fist start out and see if that makes a difference.....