Question My PC is acting up suddenly, please help

[Maurice97]

my PC is an older gaming machine that I built back in 2016 and it worked flawlessly til now.

i7 4790,
RX480 8gb
16 GB ram,

Nowadays when I try to power it on it does absolutely nothing but if I leave it and come back perhaps after an hour or so it powers up mostly fine, it also tends to throw CPU fan error white the fan is working well, it idles around 1000 rpm

Also last night it refused to turn on with the graphics card connected but right now it's connected and working well (well after leaving it for an hour or so, so it turns on)
So what could that possibly be? the power button? motherboard? PSU?

 

[rgd1101]

make and model of the psu?

 

[Maurice97]

make and model of the psu?

I don't remember the exact model but it's a Seasonic 620watt 80+ something

 

[Maurice97]

Fixed the power issue, simply replaced the power button
Still having problems with CPU fan error