Per the owner's manual:

 

Mine does this too, just going through checks when starting up like the differrent lights on the instrument panel

 

Perfect question and an answer...let's see if this one goes off the rails too ?

 

It will also flash if you come up on an object too fast or something in front of you. Saw it a few times while driving, mostly when someone cuts me off too close. Otherwise its the self check at start up

 

 

Mine comes on whenever a idiot decides they want to jaywalk and stand in the center median mear inches from my vehicle as I whiz by them at 45 mph.

 

GMC has hud available so it has info showing there whenever its running.