Question Problem with POST

[hysten]

Hi. I have a problem with my PC which started recently. When I turn on the PC (after been Shut Down - not Sleep), there's power to all devices but the PC won't go beyond POST and the beep is not heared. When I press the reset button (while the PC is still on), there's the Post beep and it boots up normally. If I put the PC on sleep, and then turn it on, it turns on ok beyond POST.
I tried another hard drive with another Windows 10 and the issue is still the same. I also removed all hard-drives and it won't go beyond POST. I noticed that sometimes the PC is taking long to recognise the hard-drives. Could it be a Power Supply issue?

Thank you!

 

[rgd1101]

full system spec? include make and model of the psu

 

[hysten]

Full specs:
Motherboard: Gigabyte Z97X-Game Plus
PSU: EVGA 600b (600Watts)
CPU: Intel Core i5 4670K 3.40GHz Socket 1150 LGA
RAM: 16GB DDR3 (2x8GB Corsair Vengeance — 16GB Dual Channel DDR3 Memory Kit)
GPU: NVIDIA GeForce GTX 1060 6GB
Hard-drives:
Seagate 3.5 inch Barracuda 1TB GB 7200rpm Mechanical (ST31000524AS)
Seagate 3.5 inch 3TB Mechanical (ST3000DM001-1ER166)
Samsung 860 EVO 500GB SSD
Operating System: Microsoft Windows 10 (10.0) Professional 64-bit (Build 18363)