Question Possible dead PSU

[Pixelatedfont]

Hi, recently I have been experiencing a problem when booting up everything would turn on for a sec then turn off and repeat the cycle.
So I sent the pc to the tech and they said the problem is with the PSU so I'm thinking of getting a new one and I'm not sure what or how to choose. I hope that I can get some help here.
Here's my specs (I didn't build it myself or know how to so it could be a bad build, sorry in advance.)
Motherboard : Gigabyte Z270m-d3h.
CPU : I5-7500.
Ram : DDR4 8GB
GPU : GTX 1070 G1 Gaming.
SSD: Samsung 850 Evo M.2.
HDD : 1TB Seagate.
Current PSU is FSP Saga 650w

I hope that is enough, thank you for your time.

 

[Dark Lord of Tech]

AC Power Loss Restart settings in the bios , WHAT ARE THEY SET TO?

 

[Pixelatedfont]

AC Power Loss Restart settings in the bios , WHAT ARE THEY SET TO?

I never messed with the BIOS beside setting up the SSD with the HDD and that was 2 years ago and right now I can't access BIOS to see the setting you mention given the circumstances.