I have had issues periodically with starting my 05 Grand Cherokee Limited.
I thought the battery(brad new optima yellow top) was dead and boosted but no go as I would get lights etc all worked but I could here a click : like a selenoid. If I turned the key back and forth many times it would finally start.
Took it to the mechanic and he tried it 10 times and it always started without a glitch. Two weeks later same darn thing and I had to turn the key back and forth 50 times ,. Each time i could here the click up in the engine until it finally started.....could it be the starter relay??
In my WK 5.7 I had the starter replaced under warranty several time and my starting issue went away. It never made any real click noise. After warranty I had the same issue again and if I crawl under and tap starter it works fine for a few months or more. I think the heat shield is the issue in that it always acts up after first hot day and or a long drive. I now have a bent shaped tire iron I use the tap starter from above. I hope new Jeep come with starter tapping tool.