Rough idle at freezing cold start - 2000 Intrigue

After sitting overnight and when the temperature is well below freezing (~20C), my car has been starting rough. It turns over and starts on the first try, but the initial idle is rough: RPMs jump around as the idle increases from 1000 to 2000 rpm, and it sounds like the engine is misfiring. This rough idle only lasts about 20 seconds at which point the engine runs fine. Any ideas on what may be causing this or what I should check before the problem gets worse. I replaced all the spark plugs 500 miles ago with the OE NGK/ACDelcos.

2000 Intrigue GLS, 3.5L, 68500 miles

Thank you.

My 02 Intrigue does the same thing. It is just somthing that cars do in extremely cold weather. Oil, gas and coolant all have freezing points too. If it isnt doinng it all the time and only when it's extremely cold I wouldnt worry about it.