2000 f350 trys to start without keyor anyone in vehicle

A Starter Solenoid that is stuck will do that. A starter relay that has failed closed will too (more common to see those relays fail on the AC system but it does happen.) Does this occur out of the blue at random? Short to power in the start circuit, ignition switch??? Which engine do you have?

Out of the blue. 7.3

Look at the starter solenoid too

It is a recall on that starts a fire. Ford fix free

my 2000 f350 7.3L truck did the same thing, I was nearby and was able to disconnect batteries and save the starter. I thought it was the ignition sw and replaced it, but now I only get 8 volts to the starter solenoid from the alarm system circuit.