Won't Start & Reduced Power, CEL lit, then Fine

[Steve Mohl]

So I have a 2018 Silverado 1500 Max Tow, with about 13k on it.  Saturday morning I went out to start it, key on, everything lit up normal, turned to start, 1 loud click, no crank.  Released key, tried again, started fine, ran fine all day long.  It was about 30 degrees out.  Sunday morning, 33 degrees.  Wanted to remote start the truck.  It didn't start.  Stepped outside, thinking maybe my fob was getting weak.  Tried it again, one loud click, and nothing.  So I went to the truck, tried to start.  Key on, everything lit up normally, turned to start, one loud click, and nothing else.....EXCEPT, "Reduced Power" popped up on the dash display.  Released key, tried again, same result.  Turned key to off, removed, tried again, this time it started but ran TERRIBLY!  Shook, rumbled, felt like it was running on only 2 or 3 cylinders, CEL light on, and "Reduced Power" notification again.  Shut it off, tried again, started, ran better, still a little rough, CEL, no other notification.  Shut it off, started one more time.  Started and ran normally, CEL lit, no other fault indications.  Drove to church, grocery store, and home, ran fine, CEL remained lit.  Later in the afternoon, needed to haul something to my folks house.  Truck started and ran fine, NO CEL now.  What the Heck?  Anyone experienced anything like this?  Any ideas.  Called a dealer, they said if there was no light on, not much they can do.  Don't want to get stranded with winter about to hit....

[Lsgun1]

Test the battery.