Squealing car - thoughts?

I drive a 2008 Dodge Grand Caravan with about 30,000 miles on it. I've taken good care of it, changed the oil 4 times a year (I live in Minnesota) etc. Every now and then, and more often lately, I hear a terrible metallic squealing sound when my foot is on the gas, regardless of speed, that stops instantly when I take my foot off the gas. After a few minutes it stops, then the car smells of smoke for another minute or so. Then nothing for months. It's probably happened 5 times since I owned the car. It never happens when I'm at the dealer, amazingly enough, and they can't see anything wrong. I think it's probably some sort of bearing burning out or something but don't know how serious this is. Should I be worried? It otherwise runs perfectly.