I have had an intermittent problem with my A/C and it seems to be getting worse, but it doesn't seem to happen when I take it in to the dealer.

I have a 2009 A5 and when I first start the car, warm air blows out all of the vents when the problem is happening. It can take from 15 seconds to 3 minutes for the air to blow cold. Once it starts blowing cold, I never have a problem.

It first happened once in a 3-4 week time period, then more often lately with it now happening every day morning and night when driving home from work. The car is still under warranty, but the dealer said they never heard of such a thing and I am just trying to figure it out myself.