Mine does something... similar... First time I start the truck, no problem. If I park it somewhere for some amount of time less than overnight (not sure what the ceiling is), the infotainment system boots up, but the radio crashes and restarts continuously as long as it's on. The cell reception icon in the bottom right corner flashes in time with the radio reboots. If I shut the truck down and restart it, sometimes it'll come back on (though the percentage of the time this works has decreased and the percentage of the time it misbehaves has increased over time). I've messed around with other systems under the infotainment system's purview, but it only seems to affect these two.
I took it to the dealer, and they updated the operating system. Didn't work. Turns out, they didn't actually succeed in their update, and updates not sticking is now a known issue (according to the service guy). I took it back in, and they updated it again. Still didn't work.
My issue is clearly different than the above that GM is interested in (volume knob/toggle never touched), and different than the other two posters (just the two failures rather than across the board). As an engineer who works with similar sorts of software/hardware systems, the problem for my part looks pretty obvious... You have two subsystems similar in nature, but otherwise unrelated. They both require some sort of antenna (radio and cellular), and both of those antennae possess certain physical characteristics that put them way out away from everything else, and often on their own discreet board... For them both to fail simultaneously and in lockstep with each other tells me either a plug isn't fully seated or the antenna module is faulty. GM has not yet reached this conclusion...
More specific to you guys' issue, I believe I read a bit ago that there was an issue with an iOS update that was causing problems like this. A simple iOS update would resolve it. I could be misremembering, but check for phone updates and report back.
