Q: I have a loud squealing noise that is intermittent.

Over the last 3 months, I have had to get all new brake pads and rotors (Firestone), new tires (Walmart), and had engine work done for a recall regarding engine oil consumption (at the Dealership). Four weeks ago, I started hearing a loud squealing noise when I reversed the car only. After a week, I took it in to Firestone to have them re-check the brake pads/rotors. They said everything looked fine and after 10 tries of reversing the car, they heard a faint squeal twice but nothing loud and nothing consistent. They advised me to come back once the noise was constant. Then the noise went away for a week. And now for the past two weeks, I am getting the loud squeal when I immediately turn the car on to reverse out of my parking spot and then again when I turn the wheel and step on the gas. The noise doesn't last throughout my drive and there is no engine check light showing. Any idea what this could be? Possibly the serpentine belt?

My car has 85000 miles.
My car has an automatic transmission.