2004 Hyundai Accent popping sound

When I started the car to leave work yesterday, I heard a rattle. I drove a block to the gas station and it rattled the whole way. When I started it again to leave the gas station the rattle was gone. However, when I got home and shut it off, I heard a loud pop that sounded like it came from the front. I drove to work this a.M. And it did not pop again when I shut it off. I had the defroster on when I started it yesterday, but turned it off half way home. The belts (what I can see) look ok. Actually they look like they're in pretty good shape.I think my car is a 4 cylinder, but i'm not sure. It did not overheat or anything coming to work this morning (8 miles), but i'm a little worried as I am an older woman and don't leave work until after dark and don't want to break down.