What could cause that burning smell in my car?
Oil could be oozing onto a hot part of the engine or exhaust system. It also could come from overheated brake pads and/or rotors—due either to aggressive braking, pads that don’t retract when you release the brake pedal, or the emergency brake having been left on while driving. On a vehicle with a manual transmission, the clutch plate could be worn or overheated from riding the clutch pedal. Leaves or other material in the engine compartment—sometimes imported by nesting rodents—can also burn on hot surfaces.

What is causing that gasoline smell in my car?
It’s normal to smell a little gas when a cold engine is first started because of incomplete combustion. If you smell gas after the engine is warm, though, the gas cap could be loose or the evaporative emissions control system—which is supposed to contain fuel vapors and recycle them through the engine—could be leaking or clogged. Even worse, gas could be leaking from the tank or another part of the fuel system. Always investigate gas smells you discover when your car is parked before starting the car and potentially igniting the fuel.

Source: https://www.cars.com/articles/whats-causing-that-smell-in-my-car-1420685136993/