IMO you have to fix hardware issues (to include overheating) BEFORE you can troubleshoot software issues.
The system shutting down without leaving a memory dump file is suggestive of a hardware problem.
The fact that it won't reboot for a while (until the system has cooled down a bit) is suggestive of overheating.
There aren't any indications that this is software/Win8 related (but there was the suggestion that there might be a problem with the wireless USB networking device).