I hadn't driven my car in the last couple of days. I park outside and a bit of water gets on my cars from sprinklers and it's been kinda cold lately, but no snow or anything crazy like that.
I turned my car on today and started backing out of my spot and my back brakes were squealing and sometimes it would make a really loud HUMMMMMMMMMM noise like the ebrake was on or sometihng, but it wasn't. The caris about a month old and it should be in fine shape.. After about a minute of driving the noises went away.

Any input?
Thanks!

 

likely it is either that your brakes seized up slightly with your ebrake/parking brake being on for a couple days, or you built up some light rust on the rotors that just wore off as you drove. The second is more likely in my opinion.
Stocker.

 

I agree rust will build up quickly on rotors, not a big deal as it will be taken care of the first few times you hit the brakes

 

it's mostly rust that builds up from that little water and condensation from the dew. Don't sweat it, drive the car a bit using the brakes gingerly (ie don't stomp on them) and the rust will be removed and the sound should disappear...

Enjoy your P5!!