Pc does not always boot.

[WellHello]

Description of the problem : After buying a new psu , a seasonic 1200xp3 , my pc sometimes does not boot. I press the startup button on the case , and it does not start. When that happens , i have to turn the psu on and off for a couple of times ( waiting around 1 minute for the mobo lights to turn off ) , and it will start up . To note , if i leave my pc open and it reaches the sleep state , sometimes coming back and pressing the mouse will power it back up , but other times , it will power up ONLY the peripherals ( the leds in my mouse , mousepad and keyboard start doing their rainbow-cycle ) , but not the pc. In that case , i proceed to shut down via the power supply and repeat the process described until it starts up.

Components : Xp3 - seasonic 1200W

4x8gb HyperX Fury RAM 2800 mhz 

Asus gtx 980 ( oc'ed at 1560 mhz on core )

i7 6700k ( oc'ed at 4.6 ghz , small increment in voltage )

Asus Hero VIII motherboard 

Samsung 950 pro M.2 ssd

2TB hdd ( i think western black , but haven't checked on it )

Extra information : After it boots on , it's perfect. No crashes , stable oc's ( have tried stock too , overclocks are not at fault here ) , expected performance. It probably is a faulty PSU , but it'd be strange , considering everything is fine after i get over the boot part.

[User1868]

Sometimes you just have to wait a while. The PC isn't going to be fully ready as soon as you power it up. How long do you wait before turning the PC on/off

[WellHello]

3 hours ago, User1868 said:

Sometimes you just have to wait a while. The PC isn't going to be fully ready as soon as you power it up. How long do you wait before turning the PC on/off

It's not about that. The pc really does NOT power up sometimes . It's not like the old " fans power up but then nothing happens " , literally does not start . As to waiting between on / offs of the psu , it's usually around 1 minute off for the mobo lights to go down , and then i turn it on again.

[User1868]

Did you try a different PSU?