It happens right after the car starts but, it was really cold in Florida when I started to hear this sound. Since then it has warmed up and I have not heard it since. Though I have 120k miles on this motor and its about time for a timing belt change. Some of my pulleys are starting to make noise (bearings) What I think the sound was a belt sqeak combined with some of the pulley bearing noise. I think after the timing belt is changed and all that goes with that, the car should be fine. Also the clamp that holds the air intake to the mass air meter had come loose, maybe the sound came from that. Florida cars dont like to start up in the cold not used to it. But I will definitly try your suggestion if I hear it again.