air condition problem on 2002 BMW 745i

When I start my car my outside temperature reads (-16F or lower) my air conditioner does not cool the car until it reads (+15 or higher)mind you the temperature in Maryland has been 90 degrees or higher. As the outside temperature rises the air conditioner gets colder which tells me its not freon. But the unit only works if the car is in motion.

Asked by for the 2002 BMW 745i
Did you find out why this was happening? Was there a problem with the outside temperature sensor?