PC keeps shutting down

[Kasasam123]

So I just built my first pc with a few second hand parts but my system keeps shutting down or rebooting.Sometimes it'll be a few seconds after turning on the pc and the other times ill have a few minutes, boot to windows and then it shuts down. I have tried everything from using one stick of memory, testing the psu with a paperclip and the fan still rotates, gpu being uninstalled, used mulitple plugs for psu, reseated and re applied thermal paste.

At this moment all i have connected to my motherboard is my cpu, cpu cooler, one stick of ram in the first dimm, hdmi connected to the motherboard and my motherboard is on a cardboard box. I power it on, i get to the BIOS and usually after a few minutes shuts down. I have been at this for days and in dire need of help.

 

Specs:

intel 4770k

Phantek PH-TC14CS

zotac gtx 1080

corsair force 3 

WD Black 2b

4x4 DDR3 1600 

z87 mpower msi motherboard

antec 1200w psu

 

Thanks