Its foolish to start the car and then not drive it. You do not accomplish a thing, as the engine idles, condensation forms in the exhaust system and engine. I have never done that, once its parked it stays parked. A for the winter warm up, thats not a good idea either. Runit long enough to allow oil pressure to stabalize and drive it.
Idling is the worst thing you can do to an engine, I have an elderly relative that does this a lot, she only goes up 2 miles with the Lumuna and been driving like this for a couple years. Right now, nothing but trouble with the car, its so carboned up from all the idling and short driving. The Chevy dealer has worker on it 2x this year for the same problem, they have told, Don't idle the car so much and drive more. So now every week I have to take here car for 50 mile run just to keep it out of the shop. And BTW, had to put new battery in car already, just over 2 yrs old. Idleing is good, NO WAY.