Even if the parking brake pedal indicates fully disengaged, it may not be, due to corrosion, or may require adjustment, like this: Then again, there’s this Toyota TSB based on NHTSA comments on initial brake noise when cold: https://static.nhtsa.gov/odi/tsbs/2013/MC-10132090-9999.pdf
Only backing up... could be normal. Steps to reduce brake squeak include: 1) Deglazing the rotors. 2) A few high speed stops, with cooling between stops. 3) Reapply anti squeak "grease" to the pad backings. 4) "Blue Printing" the pads. Good luck
Thanks guys! I guess it's not too serious then. When it goes in for maintenance, I'll ask the tech to check it.
