My only theory would be the temperature causing your issue. Since it is that cold, your oil is a thicker hence your motor working alittle harder when very cold. My car has somewhat experienced your issue in the past and what I do is just crank the motor 1-2 seconds a little longer and my car doesnt do the problem as much

__________________
2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6