Car may not restart appears it ran but computer shut it down

fuel filter needs replaced or fuel pump

Change the ignition lock.

Bad computer ,brain ecm

How old is the fuel in the tractor? is it petrol or diesel powered?

Have the check engine codes been checked ?

I would pay more attention to the air flow sensor and mass air flow sensor, putting this on a diagnostic machine will pinpoint the errors stored on the onboard computer. both sensors can be cleaned by a competent mechanic, most mechanics don't want to, they prefer just to swap items out these days because of costs. get a reading, then you will know for sure. good luck.

I recently came across a similar situation in a isuzu that took some time to diagnose. What if eventually turned out to be one injector had an intermittent failure and it too out 2 other injectors and the engine shut down. If the vehicle sat for 1/2 hour it restarted and ran again for sometimes days before the fault again appeared. It was tracked down by running the truck on a chassis dyno under load and when the fault appeared each injector was disconnected until the faulty one was revealed. If these symptoms parallel yours I suggest you point the mechanic in that direction .

pres.reg.or TPS

It could be something as simple as a bad or loose ground wire but the hard part is finding it.
Good luck
Sam

check the engine ground strap