* Electrical shorts: A faulty wire, corroded connection, or damaged component in the electrical system can arc and ignite surrounding materials. This is especially true if the battery is still connected.
* Fuel leaks: A leak in the fuel system can allow gasoline to accumulate and ignite from a spark (even a small one from a static discharge) or heat source.
* Overheated components: Even with the engine off, things like the catalytic converter can still get extremely hot after being used and remain hot enough to ignite nearby flammable materials.
* External sources: A nearby fire, discarded cigarettes, or a carelessly placed heat source could easily ignite a car's interior or exterior.
* Spontaneous combustion (rare): While incredibly rare in cars, spontaneous combustion from oily rags or other materials left inside is theoretically possible.
Therefore, while less likely than a running car, a non-running car is not immune to catching fire.
