I installed an msi gtx 1070ti and everything was working fine for about a week but recently my computer has been shutting off and restarting. This happened before with a 1070 i bought a few months back and had returned as well (exact same problem). For some reason the computer runs fine with the integrated gpu (530) in the motherboard. I have tried reassembling my computer and reinstalling all my drivers. Not sure what to do as I do not have a spare motherboard or psu to test for defective parts. I do not think it is the gpu itself since the same issue happened with the 1070 i bought a few months back. Nothing is overheating either, everything seems to be working fine until my computer shuts off without warning.
msi gtx 1070ti 8gb titanium (the old gpu i refunded was msi 1070 aero)
msi z170-a pro solution intel atx motherboard
Corsair RMx series rm850x 850 watt fully modular psu
Windows 10 pro