Do you worry about spontaneous combustion of ICE cars? They are far more likely to burst into flames than EVs.
There’s a substantial increased risk only with ICE cars that are at least 10 years old and poorly maintained. Li-ion EVs carry that risk from day one.
EVs and ICE cars can both catch on fire in a bad enough accident, but this is true regardless of the age of the vehicle, and tends to be more sudden and violent with gasoline explosions vs battery fires.
No. They can happen with manufacturing flaws, wear and tear, or with a dent to the underside of the car in case of EVs too.