I have experieced this condition twice. Both times it was below zero degrees outside and I parked my 4.8is in a heated garage. With the car perfectly warm from being indoors it will run poorly and misfire at startup.
I mentioned the condition at the dealership after the SES light came on during the rough idle and was informed it was a MAF sensor fault but the sensor was good.
I was advised to let the engine run for a bit after entering the heated garage so the sensors have time to register the temp change before shutting it down. Apparently this helps somehow.

So far, no more trouble.

__________________
2005 4.8is