Update:
It finally failed to start while at the dealer. They looked at the system on their laptop and all the diagnostics were ok. Then the tech opened the hood and checked the fuse box. He popped out the starter solenoid and put it back in and the vehicle started. The next day they replaced that solenoid and its been working ok since then. That was about 2 and a half weeks ago, so (fingers crossed) I think they fixed the problem.
Thank you to all who responded with suggestions for this. I appreciate your help.
