Computer auto reboots

[jackson6643]

l Processor Intel Core i5-6600k l l Mainboard Asus Z170-A l l Graphics Card Zotac GeForce GTX 970 l l Memory Kingston DDR4 16Gb l l Display Dell U2415 l l Storage Seagate barracuda 1TB HDD/Samsung 850 EVO SSD 250GB l l Casing Fractal Design Arc Midi R2 l l PSU Superflower Leadex Platinum Full Modular 550W l l OS Windows 7 Home Premium l

This are my specs.

I have already tried to RMA my gpu, psu and motherboard. All have no issues and my motherboard was replaced 1 to 1 due to bent pins.

I changed my cooler from a hyper 212x to a corsair h100i. Issues still here.

It autoreboots when i try to bench my system by running 3Dmark.

Temperatures were unstable jumping from 34c to 57c.

Cleaned my graphics card drives but issue still here.

Pretty torn on what else i can do, would love some help.

Thank you!