It could also be "Piston Slap". This is more of an issue for the 3.4 engines, but it's not unheard of for a 3.8 to have that issue. Mine has this quiet "tick, tick, tick" sound when it's cold, (maybe dry lifters or even valve rockers?) but goes away after the car is warmed up. I can only hear this noise when the hood is up and I'm right next to the engine, though. If I had the "Piston Slap" issue in my car, (3.4L), then it would probably be a lot louder than it is.