[John Card]

Do you have a volt meter? If you do, you can test each switch individually and see if one of them is intermittent. You can also check power going to the starter solenoid and see if power is making it to the starter. Any of the switches could be bad, the solenoid could be bad, or the starter could be bad. A meter will allow you to rule stuff out. A schematic from SPF would help - even if someone just hand draws it. Then you'll know how the system is set up and what to look for.