Hi there,
sorry to read about the issues you are facing as I have been encountering a few issues with my own system recently.
I am running an older Ryzen 7 1800X with the Gigabyte GAZ370-Gaming K7 (Rev 1.0), 32 Gb of RAM and a Palit 1050 Ti Kalm GPU. for over 3 years.
Just over 10 days ago, I powered down the PC, as I do every evening. But, in the morning when I went to power up there was nothing. No lights, no fans, it was absolutely as dead as the proverbial dodo. Fitted a brand new PSU (I was using a Corsair HX750i) but there was still nothing. I popped out the motherboard battery, cleared CMOS, fitted a new battery to the motherboard and hey presto, the system fired up. I had to reset BIOS but, once I had, the system started and ran as if nothing had happened. So, I thought, it must have been the motherboard battery that failed.
Five days after thinking I had sorted things out, I faced exactly the same dilemma. PC working fine all day, powered off over night, nothing when I went to switch it on the following day. Once again I removed the motherboard battery, cleared CMOS and then the system fired up as it had done previously.
I still haven't fully examined all of the possibilities as to why this has occurred but, I am beginning to think that, an issue between BIOS and Windows 10 may be the cause. Why do I think this the only part of my PC and environment that has changed have been Windows updates. There is no new software or hardware involved. Over the past few days I have been tweaking various things in BIOS, after doing tedious amounts of research online.
The one common factor that I discovered, was the advice to disable the CSM Support if running Windows 10. I have done this and so far, my computer has been running OK.
It might be that you are facing a similar situation so what I would advise you to try are the basic steps that I took. Disconnect the PC from the mains power. Pop out the motherboard battery and clear CMOS (this will mean that you will have to reset BIOS). Put the motherboard battery back and then see if your system will start.
If it doesn't, you haven't lost anything and you are a step closer to finding the solution. If it does start then, when you are resetting BIOS, disable the CSM Support and see if that helps.