This happened to me last month, on the way home from florida.
We fueled up in a flying J, and when I went to restart the rig, nuttin, nada, zippo.
Dash all lit up like it was supposed to, trans pad lit up, wait to start went on then off, but nuttin when I turned the key.
As we were stuck at a truck diesel pump in a busy flying j, I had them call the mobile truck fixer guy.
I had him crawl under with a screwdriver and jump across the starter solenoid, and she fired right up.
Next night was home, so I just didn't turn it off the whole way.
Since then, I've cranked and started the rig several times, no problem.
I suspect the ignition switch, but there is also a small relay in the circuit, and troubleshooting a problem that isn't happening isn't easy.
I may just crawl under and hookup a remote start pushbutton, put it in a storage bay, just in case. Or go with Don's method and just replace the ignition switch.
Or both.