Hi all,
I'm facing a very unusual problem & not able to fix it. Appreciate your help on this.

My Specs
CPU        BX80646I74790K         Intel Core i7-4790K 4.0GHz Quad-Core Processor (Overclocked stable to 4.4GHz with 1.25v)
Cooler        ELC-LT240-HP        Enermax LIQTECH 240 AIO Liquid CPU Cooler
Mobo        152-HR-E979-KR        EVGA Z97 Classified
Mem        F3-2400C10D-16GTX        32GB G.Skill Trident X 32GB (4X8GB) 2400Mhz DDR3 (Overclocked to XMP Profile1 with 2400Mhz with 1.65V)
GPU        06G-P4-1996-KR        EVGA GeForce GTX 980 Ti HYBRID GAMING (Overclocked to 110% power limit, 135mhz core clock & No memory overclock)
SSD        SDSSDXPS-240G        SanDisk Extreme PRO 240GB Solid State Drive
SSD        SHSS37A/480G        Kingston HyperX Savage 480GB
HDD        WD1003FZEX        WD Black 2TB SATA 6 Gb/s, 7200 RPM, 64MB Cache
PSU        SNOW SILENT-1050        Seasonic SNOW SILENT 1050W ATX12V/EPS12V 80 PLUS Platinum

Bios Version is 2.04 because the latest 2.06 crashed my PC & rolled back to a version just before specter.

Problem1 - When you press the power button the PC wont POST/BOOT. After a while maybe 10mins sometime 1hour later. The PC will boot up.
Problem2 - Sometimes even after you press the button the PC will not boot at all.

Solution Checks
1) Checked power cord to PSU & replaced with a new one
2) No change in hardware made during 4yrs of setting up this PC
3) Windows 10 has always been updated automatically
4) Removed the AIO cooler & Memory sticks, reseated both and used a ceramic gel for AIO
5) Tried BIOS 1, 2, 3 at Stock and Overclocked both had same results.
6) Removed all USBs, Headphones, All points from motherboard & tried posting. Didn't work.
7) Changed the CMOS battery to a newone (Duracell)
8) Checked PSU power to Motherboard & Power to MB is present as the Red light for BIOS & White-light on the MB lights up when you turn ON the switch on the PSU.

So I have finally runout of solutions or ideas on how to find the root cause of this. Kindly help as I've gone through the entire forum to find a problem like it but noone has such an issue. My warranty expired for the Motherboard & GPU so unable to raise a ticket anymore. Appreciate your help in finding the cause & a way to fix it permanently.

Hi Sajin,
I disassembled the PC while swapping RAM DIMMs. So during that I tried removing the GPU & booting. Sometime it boots fine & sometime it doesn't. How to test it's a PSU issue. I have a 1000W Seasonic & never failed on me. If it's a PSU issue then there shouldnt be any power at all right?
Paul

I'm raising a ticket with Seasonic since it's in warranty. Let me see what they would come back with. Will come back with an update on this thread. I dont have a second PSU to test. But If i need to buy one which Platinum 1000w PSU would you recommend in 2019.

I've had bad DVD drive give this type of symptom ... removed drive & it booted normally
 
Unplug the Case connections & Test ... maybe a faulty start button or wire ?
 
Remove everything ---> except Boot drive & test
 
Still not working:  MB out of case & on cardboard --> in Minimal form
 
Older MB -- could be a "tin whisker issue"