Light Grinding Sound While Accelerating At Low Speeds

So water pump was replaced a few months ago, blower motor was replaced a couple of weeks ago (that one was actually almost as easy as expected!), a new set of tires about a month ago ... and unfortunately a new worry. Trying to see how worried I should be.

Just recently started getting a mild grinding (or perhaps chittering) sound when accelerating at low speed. Seems to disappear at higher speeds. Hoping perhaps a problem with sticking brakes or something that *might* not be too worrying.

But exactly once, had it at a time that brakes made no sense. I was at a stop light, the car was in gear, but I had the brake depressed (because red light). And it was doing the same grinding sound. I switched the car to N, and the sound stopped. Put it back into D and it was chittering again.

But only at that one stop, not any other time I've stopped. So I'm kind of confused.

Trying to figure out possible issues, while trying to earn enough money to make it in to the dealership and get things checked over.