I think the Gos have a thermal problem. The first one I returned for the one I have now and it does the same thing. They both have sometimes froze up and have to be rebooted occasionally. I still like the head set, I wonder if a light weight heat sink could help.
Oculus Go should not overheat under normal use. Is your house or area very hot? That could have an effect. Or if you charge it while in use (you shouldn't do this). The face-plate on Go is a heat-sink, you shouldn't need anything extra.
FWIW, I've only gotten the overheating message twice.
Once when I plugged it into the wall charger when I was running out of battery during a long Catan game. (I since switched to using a power bank during Catan games that are longer than the internal battery life, and that seems to keep it from happening.)
Once when I put it to sleep & on the wall charger without exiting the current app. When I picked it back up later, it was complaining about over-heating. Because the thing wakes up so easily...like when you're covering the lenses. So now I always make sure that I leave the current app and—after covering the lenses—tap the power button again if I hear it wake up & make sure I hear it go back to sleep.
So, the overheating you're seeing certainly doesn't seem to be endemic.