Random shutdown

[Raouws]

I've been experiencing some really really odd behaviour in my PC.
it started only recently, and it happened like 4 or 5 times up until now.

Im just doing my business or whatever... watching youtube videos, working on some graphics or some thing
when suddenly out of no where or what ever reason i get a shutdown. power goes off completely.
after 2 seconds power goes back on expect no hardware jumpstarts, the only thing thats on is the power LED on the case.
every thing else is not starting. I hold a long press on the power button, every thing goes completely off, i press power again and nothing happens expect the power LED turning on again. After i open my case and remove the GPU, check all the connections and re install the GPU, suddenly every thing start normally again. I've tested the GPU and PSU, there are no apparent sings of hardware failure what so ever, there is hardly any stress on any of my PC components in daily use.

I'm running Mac OS 10.13 (17A405).
This issue NEVER occurred before, any ideas on whats going on?

 

[Raouws]

update:

Testing with a backup PSU seems to reveal that my original PSU gone bad.
i'm not sure how or why it happened... but i guess my only option would be to take it to the lab for some testing.
It was always kept clean and dust free, so it cant be anything related to dust.