Funny Smell

I just noticed this today. After driving for 10 minutes or so I and my wife smelled what seemed like burnt rubber or plastic. I think it was more of a burnt plastic smell. At first I thought it might have something to do with the serpentine belt. I looked at it but it looked fine. I am worried that some rotating part is rubbing on something else. Any suggestions???

Check underneath the car.
It is very possible that a plastic grocery bag or other type of plastic bag is lodged underneath and is being melted by the exhaust.