Diesel engine won't restart when hot

Start with the basics. When was the fuel filter last changed?

The fuel filter is probably a year old to 18 months old. The engine doesn't cut out so I was thinking it probably was not fuel related, more electrical. However you guys are the experts. Is 18 months too old for a fuel filter?
If you have a minute I would love to learn the logic behind your question. How could the fuel filter be affected by the engine being hot - I just don't get it.
Thank you for responding tho'

You have high miles on this vehicle so theres a chance of wear on the fuel pump both electrical and mechanical. A restrictive fuel filter can cause the electric pump to overheat. And the fuel filter is too often neglected. That said the time frame seems acceptable, though every 50 to 60 thousand miles is the rule of thumb for a change. Diesels run only on compression, so theres no spark plug. The only electrical that would heat up and prevent running then in this case is in computer control of the injectors. Always good to start with basics first in any case. Make sure your charging system is charging after getting hot as well. The whole car depends on it