My battery died after 2 ½ years, 13,000 miles on my 2014 LTZ 5.3L. It acted very strange with slow crank several times and then wouldn't start. It would jump start and run, but never restart without "help". I put it on a charger / tester which said it was completely charged and nothing wrong, but as soon as I opened the door, the voltage would drop quickly. Radio also was acting weird. It would not stay on a station properly and would not let me select a favorite until it ran a while. A lot of hissing and popping like a AM station does during a lightening storm, but it was FM.
Took it to the dealer since it is still under the bumper to bumper warranty. They rested it and said CCA was only 151 instead of 720. Replaced battery under warranty.
chuckl1218's post in 2014 Silverado Random Dead Battery - now will not stay charged was marked as the answer