Ignition switch is a common failure on this vehicle......Next time problem happens access wires going to igniton switch. Red wire shoudl have voltage at all times and yellow wier shoudl have votlage when key is in start position. If only red wire has voltage replace ignition switch. If good you will need to see if pcm is grounding starter relay....If so but starter relay isnt clicking replace wire between relay and switch......IF pcm isnt grounding starter you will need to check for codes in body control module. here is a wire diagram, let me know if you have questions. Thanks.
So far the car always cranks at the repair shop, so unless the car doesn't crank the switch will test good?
You will need to wait until it doesnt start to do tests.....Then follow voltage from the ignition switch to the pcm to the starter relay to see where it drops off at. Let me know if you have questions, thanks.