Auto climate control
 

I have a 2007 CTS base model for about a year now. Coming on winter here again in Canada and trying to figure out this Auto Mode as the owners manual kinda bland.
Issue is I will put the climate control in manual mode let's say on defrost, set at 90F fan speed 2. All works fine and dandy. Left that setting on i will shut car off and later either start with key or by remote start and when I get into the car the climate control is on AUTO, barely warm and fan running at low speed. I can set it back to manual mode and have no issues but wondering why car is automatically setting to AUTO mode when it wasn't left that way when car shut off?
All other functions of the climate control work properly and with no issues just this. It is a pain in winter when -30C becasue the AUTO mode takes forever to heat up interior as it slows fan speed down due to the cold weather and will eventually speed it up after interior warms up enough(usually 25mins).
Any help will help.