After the car warms up and idles at temporary stops like traffic lights or stop signs, there is a noise at the right side of the engine compartment - like something is vibrating. The noise occurs when the car is in drive and in reverse but not when it’s in neutral or drive.
Well it likely is something that is loose. You need to follow the noise to the source. You can use a length of garden hose like a stethoscope if needed.
Good Luck
Have driver in driver’s seat. Have engine on, and put into drive or reverse. You, position yourself near source of noise (hood up). What, and where, do you hear noise? Show and tell.
It Could Be A Loose Exhaust Heat Shield Or The Guts In The Catalytic Convertor Breaking Up
At a time when it makes the rattle, stop and shut off the engine. Go kick the tailpipe from side-to-side with a couple of swift little kicks to set it jiggling. Do you hear the rattle ? If so, it’s probably the exhaust system. Then scrutinize that system. If not, check any and all motor mounts and engine anti-roll gizmos.
CSA
Thanks for the comments. I was afraid it might be something expensive.
Exhaust heat shield=very cheap to fix
Motor mounts or catalytic converter=not cheap to fix