I have a 2002 Intrepid ES (3.5L)... usually when I start the engine (from a cold start only) there's a noticable andcontinuous 'flapping' noisewhich i haven't been able to exactly locate where it's coming from around the engine because of ambient noise. But it doesgradually disappearand is gone atnormal operating temperature. I can only think of it being the tightness of the drive belts due to temperature difference. Does anyone have any other ideas and/or suggestions forstoppingthis flapping noise... besides trying to adjust the belt tightness? Thank ya much.

 

My 3.2 makes that noise too, and it is a little worse when it's damp as well as cool. The noise is definitely belt slap, and requires tightening the serpentine belt. This has been discussed extensively on another dodge intrepid forum. I have been meaning to adjust mine for a long time, but it's hard to get at the adjustment, and I simply haven't taken the time.
I would hazard a guess that your 3.5 also makes a "grrrr" sound between 900 and 1500 rpm until it is fully warmed up. Same issue.