Computer shuts down on its own but the fans and led lights on the ram sticks stay running

[Camputerman]

When it first happened i took all the cables out of my pc and turned it off for a while then like 2 hours later it turned on properly and worked for 30 mins till it did it the same half shuttdown thing again. When its in the half off mode i can force shuttdown but when i turn it back on it goes into half off mode again. 
 

I disconnected my psu completely and did the paper clip check and the fans started running. I think this is a heat related issue but i think u guys would know better than me.

This build is about 4 years old but i had the psu replaced with a new one last year since it bricked on me.

 

My build: 

Intel Core i7-8700K 3.7 GHz 6-Core Processor

Noctua NH-D15 82.5 CFM CPU Cooler

Gigabyte Z370 HD3P (rev. 1.0) ATX LGA1151 Motherboard

Patriot Viper RGB 16 GB (2 x 8 GB) DDR4-3200 CL16 Memory

Western Digital Blue 1 TB 2.5" Solid State Drive x2

Zotac GeForce GTX 1060 6GB 6 GB AMP Video Card

Corsair SPEC-OMEGA RGB ATX Mid Tower Case

EVGA BR 600 W 80+ Bronze Certified ATX Power Supply