Knocking noise on 2003 Infiniti M45

For some reason or another there is a a LOUD knocking sound coming from my engine after starting it up on a cold days. It normally last for a few minutes until the vehicle is warmed up. I noticed that this only happens in the winter months when it's extremely cold outside. I drive a 2003 Infiniti M45. Please help!

3 answers
silly question, but you are using Premium Gas right? if not, I suggest you do.
It could be piston slap (loose pistons resulting from overheating, usually) or a crankshaft bearing problem. It could be some other things too so get it checked by a Nissan or Infiniti specialist.
Here's a directory link for you:
http://repairpal.com/directory?address=37172&car_brand_names=Infiniti
I have similar problems after cold cranking the car and moving it for a vary short distance and turning it off - next morning sounds like a rod bearing has gone bad - mechs indicate normal issue w/Nissan - Infiniti cars - wifes fx35 also does this.