I had a similar problem, and I opened my case and cleaned out a 'ton' of dust (4 1/2 year old computer). CPU heatsink and Video card cooler were caked with dust.
Fixed problem for a few weeks and it returned!
Seems my graphics card wasn't supported under W8.1 by ATI (Radeon HD4870), only with a W8 Legacy driver. So I bought a supported W8.1 card. Solved the problem for a few weeks.
Came back again and I was stumped. Ran MEMTEST 86+ and the RAM was OK?
My problem was that when first booted, within 2 to 15 minutes, depending what I was doing I'd either get re-booted, BSOD with varying reasons, IRQL problem (usually a driver), Kernel problem, or just a freeze. Most often when Firefox was used.
I re-installed Firefox and it continued to happen.
Then it stopped for a few weeks, this was the normal pattern, I'd do something and it seemed to solve the problem, only for it to return.
A week ago it was really bad, I could hardly boot and stay up. However, after 3 or 4 tries with it re-booting or freezing immediately for a few days, again, once that 'stopped' happening the computer worked fine for the rest of the day.
Since once it stopped and the computer ran fine for the rest of the day that sort of led me to believe it was within Windows itself, not h/w related, nor PSU (my next 'fix' was going to be replace the PSU).
So I searched the web yet again. Somewhere I found an obscure entry that was similar to my problem. Run CHKDSK, especially if on an SSD (as I am). I have 3 physical drives, one an SSD, so I set CHKDSK to run on all the drives on boot and re-booted. My 3 drives had CHKDSK run on them and didn't seem to report any errors. The system re-booted after that and then it started running CHKDSK on C: (the SSD) again? Once that was done it finally booted. I could NOT find an FOUND.000 folders on any drives nor a report that CHKDSK had fixed any errors?
However, since that was done I've NOT had a problem?
Worth trying, but I can't guarantee this will fix your problem, nor that mine will not return.
It does sort of make sense to me though, if the SSD had some bad data (those re-boots could cause it) and the structure pointers were wrong that could cause odd things to happen I guess?
Specifically in your case though I'd look at the EVENT VIEWER and see if there are some indicators of the real problem. NirSoft has a program called Blue Screen View that might help you out seeing those errors (http://www.nirsoft.net/utils/blue_screen_view.html).
Good luck.
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