Make sure the smell is burning rubber, it could actually be coolant. A lot of vehicles have problems with leaking heater cores, and this would be in line with your symptoms.
If it is a burning rubber smell then you need to carefully inspect your engine compartment. There is lots of rubber hoses in there as well as the serpentine belt, any of these COULD be your problem. Make sure nothing is out of place and touching the hot motor or exhaust. Start your car and look around to make sure all your pulleys are spinning, a frozen pulley could cause the serpentine belt to heat up and smell funny.
It's also possible that the smell is hot tranny fluid or a clutch depending on your transmission. This is not a good thing, but if it is the case it needs to be looked at and repaired before any major and expensive damage occurs.
It's probably just coolant and you have a leak somewhere.