running for some time and you shut it off it will not start again?

This is a classic starter problem but to be sure this guide will help us

https://www.2carpros.com/articles/starter-not-working-repair

Please run down this guide and report back.

My 86 Chevy chassis motorhome had the same problem. After changing the starter solenoid and adding the heat shield (recommended for big blocks especially), problem was still there.
Found out it has a 'hot start soleniod'. Looks like a ford fenderwell mounted starter soleniod. After changing it, my motorhome starts everytime no matter what.

Hope this helps, VIC
'wildfirev9'

Disable the ignition coil by removing the coil wire -Now hold key to start position and look for power at the starter solenoid small terminal with a purple wire -Power there-replace the starter. No power backtrack to the ignition switch. See below