Electrical Starter issues 2009 G8 GT

[Ole']

When my 2009 Pontiac G8 GT has sat for an extended period of time (a few hours or more), when I turn the key to start the car, I just hear a click, instead of the starter engaging and the engine turning over. It doesn't happen all of the time, maybe once or twice a week (I don't drive the car every day).

The starter was replaced a year ago. The battery is less than a year old and is fully charged. I have swapped the ignition relay in the fuse box with another matching relay used for other systems in the car. Once the starter finally engages, I can turn the car off and restart it over and over again without issues, which makes it difficult to troubleshoot. I took the car to a shop about a year ago to get maintenance/transmission flush and had them look at the starter issue and it never happened once while the car was there.

Any ideas? Maybe the (key) Ignition Switch. I don't want an intermittent issue to turn into a dead component when I am on a road trip and get stuck somewhere.