when you turn on your A/C in Auto mode does the a/c blow hot air for ~7 minutes then gradually cools off? In the lowest setting the a/c blows very cold air.
Assuming you do have a 2018 is this your first vehicle with auto temp ? If so you don’t need to turn on the air conditioner , you have it on auto and just set the temperature you want and it does the rest. Now if it does not then go to the dealer and use that warranty that was built into the price.