Another vote for slipping belt.

So... after 6 months, the noise decided to start again...
Ill probably get it checked out for sure this time... Keep yall updated.

Mechanics claim its just an over extended belt.
Will be getting car back tomorrow.
Hopefully that is it...

Downside is I'm being charged nearly $300 for repair...
$65 for belt, $125 for diagnostic fee??, $100 for labor...

Interesting! I was thinking it was the starter all this time too as my Z has been making that EXACT same sound for a couple weeks now but also only when a cold start (usually the morning.)

Has this happened since the repair a few months ago? Or is the belt the go-to resolution so I can hopefully forgo any misdiagnosis?

It was the belt, no problem since.

So about 6 months since repair, my car is starting to make this noise again on start up.
It is getting very cold here if that matters... maybe its just a coincidence.
I will wait a week and take it to mechanic if it persists.

Also, just in case... if they say its the idle pulley this time, if my new belt is damaged should a new one be covered under the standard one year parts/labor warranty? Can I argue that they neglected to properly check the idle pulley and therefore recreated the problem 6 months later? (because maybe the belt took about 6 months to stretch enough to make noise again?

I had the same noise as you. It turned out to be my starter. Had it replaced over a year ago and the noise is gone. Hope this helps.

The fact that it is intermittent makes me agree with other response of a loose, misaligned or damaged starter. Bad bearings in pulleys is possible but they usually make noise constantly and don't sound a whole lot better when warmed up but you never know. Mechanic worth his salt should be able to diagnose within an hour.

Reviving an old thread... inb4 forum warriors complain.

Did you ever find a solution to this?