Noticed coolant overflow level low so I add antifreeze and seemed to be ok just started acting up again. Overflow tank looks good.
took it to dealer at 59,700 miles and they could not get it to fail.


 

A few months too late, but you probably need a new thermostat if you have the V6. That's a VERY common issue with the LGX 3.6L engine. Also check your radiator for leaks. They also commonly fail and leaks are sometimes not obvious as the coolant sometimes dries before it hits the ground. Closely inspect the upper left corner of the radiator with a flashlight from the backside looking forward with the hood open. I have a 2021 Blazer and my leak was only visible when looked at closely with a flashlight under the hood. No coolant was visible underneath. I'm guessing I drove it for a couple months before I noticed the coolant reservoir was low.