Question Why does my computer randomly shut off and power itself back on?

[www8080]

Hi, I am seeking any help or suggestions that you guys may have for me. I have tried just about everything I can think of so far.
I have a very weird issue with my computer where it will randomly power itself back off, as if it was unplugged or forcibly
shut down, and then it will power itself back on. I originally thought it was an issue with my power supply, however,
I tried using another power supply I had laying around and the problem still occurred. I also tried it with a different
CPU cooler (I tried using the stock Intel one that came with it), I have tried replacing the CPU & motherboard
(originally had an Intel i7-7700k, today I put in an Intel i7-8700k.) I have tried running the computer with the GPU completely unplugged
from the motherboard + PSU. I have tried running it with different combinations of of RAM sticks (originally I had 4x 8GB sticks, 32 gb total)
I tried running with 16 GB (2 sticks, placed in the correct slots), and with just 1 stick which is 8GB. I have tried unplugging the power button
from the motherboard. I have tried using multiple different outlets/power sources.

Specs-

CPU: i7-7700K / i7-8700K
CPU Cooler: Hydro Series™ H115i 280mm Extreme Performance Liquid CPU Cooler
GPU: Corsair Hydro GFX GTX 1080 Ti Liquid Cooled Graphics Card
MB: ASUS ROG Maximus IX Code
RAM: Corsair Vengeance RGB 32GB (4x8GB) DDR4 3333
CASE: Thermaltake View 71 RGB 4-Sided Tempered Glass Vertical GPU Modular E-ATX Gaming Full Tower

 

[Darkbreeze]

Really? You post a question about a system that shuts off on its own, but you don't offer any information about the model of the power supply or how long it's been in use? That actually might be very helpful information to have, and be sure to provide the EXACT model number of the power supply, not just a series, brand or capacity.

And just an FYI, usually power supplies that are "just laying around" aren't much, or any, better than the one that's giving you trouble to start with. Please list BOTH power supply model numbers AND how old each of them is. Usually when a power supply is just lying around, it's because it's been replaced in the past because it wasn't doing its job then either.

 

[www8080]

Sorry, by laying around I mean I took it from my other computer. I can provide full specifications for them tomorrow, however I can tell you the original one in the build is the Corsair AX860i and the one I tried using was the Corsair AX760i. Both had same outcome.

 

[Astralv]

How often does it shuts down? Does it give any blue screens such as "Your computer ran in to a problem and we will restart it for you. Geathering information."? Did you check the error messages in Event viewer? I would not mix and match parts from different computers. The drivers are model-specific.

 

[www8080]

How often does it shuts down? Does it give any blue screens such as "Your computer ran in to a problem and we will restart it for you. Geathering information."? Did you check the error messages in Event viewer? I would not mix and match parts from different computers. The drivers are model-specific.

It's random. Could be 30 seconds, could be 5 minutes, could be 15 minutes. Could be 1 hour. Completely random and has nothing to do with the load being put on the computer, as it will happen while it is completely idle with no network being put into it whatsoever (Ethernet cable unplugged). It will happen while I am laying in bed completely away from my computer.

It never gives me a blue screen or any error code, I haven't checked any error messages in Event viewer, I will try this tomorrow.

 

[Darkbreeze]

So, you've tried two different motherboards, changing the board when you changed processors? Because you realize that your Kaby lake and Coffee lake CPUs are not compatible on the same motherboard, yes?

 

[www8080]

So, you've tried two different motherboards, changing the board when you changed processors? Because you realize that your Kaby lake and Coffee lake CPUs are not compatible on the same motherboard, yes?

Yes. Both times the CPU/Mobo came in "bundles" off Newegg, each time being compatible with each other.

 

[Darkbreeze]

Bundles don't mean much. I've seen Newegg and Tiger direct offer and send out bundles with hardware that wasn't compatible many times.

What motherboard did you get with the 8700k? Just wondering.

I think at this point I'd take everything out and bench test.

How to properly bench test your motherboard​