pc randomly restarts then keeps restarting on login


Jul 11, 2016
hello I am out of options for what i can try to figure out what is wrong with my pc...ill get right into it.

Built Pc from scratch components are:
MOBO: gigabyte z97mx-gaming 5
CPU: intel i7-4790k
GPU: nividia geforce gtx970 windforce (gigabyte version)
RAM: balistix crucial 8gbx2 ddr3 1600
Storage: western digital 1TB HHD, samsung 250GB SSD
PSU: evga supernova Nex750G 80 plus gold

after i built the pc it ran flawlessly from that start til about 3 months later where it started to restart randomly. it wouldnt happen on start up i would be on it for hours or days. at this point it would only happen about once or twice a month.
it didnt really bother me i thought it was just a rouge program or stray thread causing the problem.

as the months went on it kept getting more and more frequent once a week then a few times a week. now 6 months later it does it every one or two days but now when it happens for the first time it restarts like normal but when i login it will restart within 30s of the desktop loading or when the desktop is loading. the loop will never stop unless i leave it off or go into safe mode.

safe mode worked i would tweak with a setting or try a restore. i never went farther back then 3 weeks. even if i did not really change any settings (i went into bios once and reset the settings to default but i have never changed them. that would work for a day or so then the problem would start again. after using this method a few times it now restarts while im in safe mode also.

what i have tried to fix it:
turned off auto restart after crash and still does not show BSOD
chkdsk nothing found all good
i ran avira anti virus on multipple passes nothing found
i have ran prime95 and a gpu stress tester with no problem even with heat.

my HHD had the OS and it is where i installed and saved everything besides games and large files i used/opened the most.
at this point i formatted my SSD which just had game and data on it. i put a clean win7 install on it (i still had the OS and bootloder on my HHD).

after the install i left everything default just to see if it would restart ( i just did homework on my schools website and watched netflix/youtube). it did not restart so i decided to start pulling some files from my HHD like school stuff and some everything from my old desktop. when i did this i could click on the shortcut on my new desktop and it would run games/files from their original location on my HHD. while i doing this (accessing the HHD) it restarted and then when i tried to login to my new OS it restarted right after i hit enter to login. so i unplugged my HHD do i clean install of win7 and get the drivers off the original disks and run my pc without the old HHD being plugged in. my PC still restarts and i run a few more tests:

i do memchecker86 for 11 hours it did around 12 passes with no errors
so the next moring after memcheck is run i get on and its fine for about 2 hours i dont do anything more than look on websites and go on youtube but then it restarts and will restart while or right after the desktop is loaded.

i run a check on my SSD no problems come back.
i went into event viewer and nothing shows up besides the your pc turned off with out properly shutting down error.

i have no clue what else to try or do could it be the PSU or MOBO?
can i run any other specific tests on the compnents to see what is wrong?