I'm driving a 2007 G35 and almost every time I turn on the car and start driving I hear a quiet metal on metal scraping (can't be heard over music) while braking. This sound goes away after a few brakes and is always sounding like it's coming from the passenger rear wheel. It doesn't come back until I've had the car off for a while. Do you guys think it's the brake pad? I felt the rotor on the back and it looks and feels completely fine to me.

Could be a bunch of things. Dust shields, some piece of trash int here, brake pad, squealer tab, etc.
Jack it up and see if you can spin the wheel by hand and hear it... maybe have someone lightly touch the brakes while you do.
If not, pull the wheel off and have a look around.

Thanks for the reply! I haven't had a chance to jack the car up this weekend but I drove a little bit to "gather more data" lol. Here's what I've found:

• First, it didn't happen at all yesterday or this morning. Outside temperatures are in the upper 50s right now.

• When it was happening it would make the sound during the beginning of the drive but then stop after a few minutes or a few brake applications

• One thought I had was that this sound disappeared once the elements (rotor, caliper, piston, and or pad) warmed up. This can't be the case as I took a short trip to the gas station where it started sounding and then quieted down on the way there, AND THEN immediately once turning the car back on started sounding again. So any "warmth" in those elements would not have dissipated yet.

• Another idea I have is that maybe there's a seized piston or close to seized piston struggling to retract initially and then eventually corrects itself? It sometimes will sound even after my foot is completely off the brake which also makes me think it could be the piston.

Thanks guys!

You'll probably want to take a look sooner rather than later. If something is loose, it could be scraping in a bad way, causing some expensive damage... and if its related to the brakes, you definitely don't want to suddenly lose braking at one corner.

It happened to mine as well. it's probably your caliper sticking and has worn out your inside pad and has worn it all the way down to the metal. Change the caliper pads and maybe the rotor and you should be good to go.

^ This, OR, maybe a pad hanging up. Probably a good time to pull the calipers, clean and re-grease the sliders and pins, and reassemble. Check pad thickness, might be a good time to replace those as well.