It now takes about 10 minutes for hot air to come out when I first drive it.

Thermostat may be stuck open. Much than if it were stuck closed. Check the vent door to make sure it is moving freely. In the colder mornings it will take longer to get hot air from the vents. Have it checked out soon. Cooling systems in a BMW are only reliable for 70K miles before you should replace all components that are plastic like the radiator, expansion tank, water pump, thermostat housing. GL

Sounds like a thermostat. Bring it to a professional for an inspection and consultation. All plastic parts should be done ideally. If costs are a problem the radiator if not leaking at the time of inspection can be left for a later date. Just make sure you heed your coolant level light and don't let it overheat. Would be glad to give it a quick look if you need.