I'll go for too much gaz since it was cold outside... just try to put the pedal to the floor and hold it while cranking for at least 20 seconds...
When it'll start, don't be afraid by the rough idle or black exaust smoke... it'll be ok after 30 seconds

 

My 3.5 would occasionally start up rough if it sat overnight. Had an oil leak internally somewhere and I had to give some extra revs in the first few seconds to smooth out.

Will it even turn over? We need more info.

 

Funny, this happened to me this morning,

After a few mins found it was my negative battery lead. It had stripped out and was no longer making a good connection to the battery. Quick swap out and BAM up and running like a champ

Hope it's as simple as that for ya