I have not tried that. You may be thinking seat squeak but stopped at a light it still squeaks and I am sitting still. It definitely sounds like its coming from the engine compartment.
I was thinking suspension
I had a sound I thought coming from the engine compartment. But every time I got out of the truck it would stop.
It was not a chirp...more of a ting
ended up being a broken upper shock mount.
Keep us posted.
do you have an self exciting Alternator?