At a stop, automatic transmission
Is in drive, with foot on brake. Has a rattle but it is not brake drag
This rattle goes Away then you drive, or when you put the transmission in neutral.
Always comes at idle.
Car drives okay. Rattle goes away after engine warms up.
Seems like a body noise, loose fender shroud . Hard to open the
Hood and check, because the car must be in gear, and foot on the brake for
The noise to be exposure.

Perhaps the rattle doesn't go away when you drive, you just don't notice it as much...

Maybe it's part of the exhaust, a bit loose.!

I have a manual that makes a similar noise but it's the alternator belt that needs changing.. could this be it with yours!!