Car starts shaking and wont go over 40 mph horrible smell

Tough to call it without looking at the vehicle. A few ideas or places to think about. A clogged catalytic converter (might smell like rotten eggs) could be an issue. Locking up brake calipers would cause a pungent smell but i would think you would see some smoke from one of the wheels. It could also be running in some sort of limp mode. I would tow it into a shop for a proper diagnostic being the majority of the issues that it could be may increase the cost of the repairs that need to be made if left unattended. Not to mention engine failure or a safety concern. Hope that helps and good luck to you.