What's the behavior of the car? Does it crank? Does it not fire, or does it fire by not stay running? Also, how cold are we talking here, below freezing? Is the check engine on?
A 2005 is a drive-by-wire system, so a lot of the behavior is computer controlled. There's no spark plug wires, it has coil packs over each spark plug. Even if one went bad, it will still run. If there were spark plug or coil pack problems, it will throw misfire engine codes before you really have problems with it starting. I've run my car with one coil pack off, and I've fouled out my plugs before, and in both cases, it didn't care about the cold, it just ran a little rougher and threw misfire codes.