There is this annoying sound coming from, I believe, dead center below my backseat. It sounds like something is lose, screw is lose, pipe is lose. I don't know.

The sound is not there all the time, I can't seem to replicate it consistently. It seem to be the first 30 minutes of my driving ONLY, and seem to be coming up on highway driving where I am going above 50-55 miles an hour.

What part is in that area of the car? Anyone has experienced this before?

Thanks for all the help I could get.

Acura CL-S 2001.