I don't drive my car in the winter but I do fire it up once and a while so the battery doesn't die and to free up the rotors, etc.
I decided to start it up this morning on maybe the coldest day all year, it fired up like normal but then gave me a "Change Oil Light Soon" indicator. I'm guessing this happened because it is so frigid cold and it hasn't been run in a while (about a week and half). I didn't run it for too long because I got worried. It smelled different. Could be that car was covered in snow and was just exhaust smell... I don't know.
Did you check the Info to see if the % was low? You could have been close when you parked it and you just happened to go over the line. It is supposed to be smart enough to lower it faster for cool weather starting, but don't know how accurate its logic is.
All cars smell odd from time to time. How all the sensors interact with impact the exhaust smell. You probably just hit the magic combination for that start.