First, this is the wrong forum for that vehicle!
If you have a leak around the valve stems, this can put some (it doesn't take much) oil in the cylinder, and that gets burned off during a start. It's 'extra' fuel, and can play havoc with the mixture. If it isn't too bad, you might not notice a blue cloud of smoke from the exhaust, but it may be enough to affect that. Has your oil consumption gone up lately?
There are lots of things that could cause this symptom...a leaking vacuum hose, various sensors including the O2 sensor. Since this is the F07 forum (GT), and none of this model are as old as yours, people here may not have any other wisdom on what to look for - the F07 first came out in 2010 model.