The ACC system is set up so that in the event of a failure, the car will go to full heat and defrost. This is sort of a safety net so that if the system does fail the windshield won't fog up. Possibly for some reason the ACC isn't getting power when the car is cold, like maybe a crack in a fuse, which starts to pass power after it's had a chance to warm up? Don't know what else to offer, except maybe some cracked solder joints in the control unit (push button panel). I'd start by replacing a few fuses.