Question My newly built PC boots up, then clicks off ten seconds after, and repeats.

[grzzy]

Hey all, this will be a sort of long post but I have nowhere else to ask. My specs will be at the bottom.
I’m new to PC building and have almost completed my first PC. Following several tutorials and hours of building I managed to put together a decent looking mid range gaming PC. However, before putting on the side panels and installing the HDD, I decided to turn it on to check everything works fine. That turned out problematic.

When I turn on the PC the fans (one rear, two top and one front, plus stock CPU cooler) spin, the front RGB lighting works (the case is an Aerocool Shard), and everything seems to run. Then after around 10 seconds an audible click can be heard and it turns off, followed by restarting and repeating this, in an endless loop.

I have two additional concerns regarding this. First of all, my RGB ram (Corsairs Vengeance) doesn’t light up when I turn the PC on, however I’m not too sure if this is because the software isnt installed to control the lighting. Secondly, my CPU power cord doesn’t seem to fully fit. It is splittable, and one side of the split cable fits but the other doesn’t. Is this normal?
Any help is appreciated. I want to play!
Thanks

SPECS:
CPU: Intel Core i5 9400F
RAM: Corsair Vengeance Pro RGB
Mobo: Gigabyte B365M H
PSU: Corsair RM550X
SSD: WD Green NVME
HDD: Seagate Barracuda 2TB
CASE: Aerocool Shard
FANS: x2 top Cooler Master x1 Rear Aerocool, x1 front Cooler Master

 

[Lutfij]

Welcome to the forums, newcomer!

You forgot to mention the make and model of your discrete GPU. The reason I brought up discrete is due to the fact that the F series of processors from Intel, lack the iGPU, so you won't get video output from the motherboard's display ports.

Also, did you try powering the system with a discrete GPU while breadboarded, without the additional chassis fans(only the bare minimum)?