Is this a PSU issue? PC restarts from wake and It takes 2 attempt to start

[Beetoz]

When I turn on my pc i can hear the computer run, case fans spins, led on. no debugg code from mobo.  but the screen is black (and monitor ON led going dim to bright on a repeat) it has input because if I unplug the monitor Dp cable the monitor says "no input found and monitor will turn off in 30 seconds" I then plug the Dp back and the screen goes black (with LED going dim to bright on repeat)  . restart button doesnt do anything. power button doesnt do anything ...so i force shut down by pressing and hold power button for 5 seconds.
then press power button again and pc runs again and now the screen works but stays on the Bio screen longer than usual . around 15 seconds that says "Please press DEL or F2 to enter UEFI BIOS setting" (normally is around 2 seconds) ( see picture)
then when it goes to that 4 blue window screen .. the spinning circle dot appears laggy/choppy and finally goes into windows screen and everything is normal (see picture)

And when I put my pc to sleep and when I wake it up, it Restarts or Shuts down and when it reboots it stays in the Bio screen for longer than usual again. like 15 seconds .. exactly as the sympton mentioned above.

It sometimes wakes up fine with the keyboard. but then the keyboard doesnt work at all. i have to unplug and plug keyboard again and it works

Mobo has the latest firmware

I have been reading around and people says it could be the power supply or this specific power supply causes problem with GTX 970? ... My seasonic X-760 is around 10 years old but im a light gamer and never leave my pc on overnight

another thing is when the problem mentioned above happens and when it finally.goes.to windows.. i can open chrome and hit Control Shift T ... all my windows tab e.g 10 browser screen is still there ... so i dont know if that makes sense ..  also the time and date doesnt have issue either

Here is my pc specs

Mobo: Asus Z97-A
Cpu : i7 4790k stock with NH-D15s
Gpu : Asus Strix gtx 970
Ram : G.SKILL Ripjaws 2x8GB) DDR3 2133MHz (xmp)
Sound card : Creative sound blaster Z
SSD : intel 520 120GB (C) , WD Barracuda 1TB (D)
Psu: Seasonic X-760 gold 80 modular
Case : Lianli lancool II Perfomance
Key-Mouse : Corsair.K70 - Razer Deathadder V2
Monitor : Dell S2721DFG 2K 165HZ ips
OS : Windows 10 pro educational 64 bit