Depends on the temperature. At 44F, I start the vehicle first thing after getting in, then buckle seat belt, pick music, check that mirrors are right, no warning lights on dash, look around to make sure no fast moving pedestrians that weren't nearby when I entered the vehicle.
At that point, 20 seconds have gone by. If it is 44F I drive off at normal speed. If it is below freezing, I drive off at slower speed for another half a minute. If it is around 15F or lower, I let it idle for 1-2 minutes before driving at slow speed.
If there is also frost or ice on the windshield, I wait however many minutes it takes to melt most of it, will use windshield washer fluid to speed that up if in a hurry, unless the vehicle tries to run the wipers when the washer pump is ran, then don't want to risk tearing wiper blades if frozen to the windshield. A little dry silicone spray on them a few times a winter helps keep ice from sticking, as does teflon blades. If I expect sub-freezing temp precipitation and have the opportunity, I fold back the wipers off the windshield instead.