Most cars have a safety feature that prevent car from accidentally "rolling". Its called the "interlocking brake system". stepping on the brake before you try to put it in gear might work. there could be a problem with that feature if it still does not work.
because its on fire
Take it out of reverse.
maybe ignitoin or ignition switch
If your battery is dead it wont come out of park. it has a solenoid that has to release ,if battery is dead it wont. hope this helps.
Either your starter or ignition..
It could be thjat it is not in park. If not put it in park it should start right up.
If the vehicle has a security feature check the fuse under the hood. My 2001 SL1 had that problem. its like a 30 Amp fuse.
crank sensor is bad
Yes, this is possible.
Then turn it off after it is put into park
Does it Crank but not start? Yes: Replace your Crankshaft Position Sensor. This is located above the starter.
BAD SAFETY SENCOR