It does happen and seemingly for no apparent reason.
3 years ago a neighbor banged on the door of my stick and bricks screaming your cars on fire.
Well, my sons 2002 Hyundai Accent was sitting there parked and it suddenly burst into flames in the dash area. Within a minute it was one big fireball as my son and I watched in dismay as windows exploded and the thing destroyed itself.
By the time the fire dept put it out, it was gutted.
And it wasn't arson.
I examined it before they towed it away and could tell it started in the dash area, near the steering column.
Chalked it up to a wiring short in possibly the high beam lever.
It can happen easy enough. All it takes is a defective switch, abraded wire or something similar.