BIOS Issue£ No restart until CMOS cleared.

Hello,
    I have an ASRock Z170 Extreme 7+ motherboard running American Megatrends BIOS P2.60.   Lately I have been experiencing a problem when trying to restart the computer. If I use Windows to restart (say to apply an update or otherwise), the machine gets hung trying to restart. The ASRock logo appears then a small underscore character sits in the upper left of the screen. I then shut down the power supply on the switch in the back and attempt to turn it back on and nothing happens. The power supply seems unresponsive to turning on the motherboard but it does power up some connected USB peripherals (like connected USB hard drives). The only way I have gotten around this is popping the lithium battery for the CMOS and waiting about 30 seconds for everything to clear and then restarting the machine, setting time and date (nothing else) and then it seems to start back up.
The reset and power buttons on the motherboard do not seem to do anything, nor does the clear CMOS button, but from what I understand that clear CMOS button is only partial clearing of CMOS settings(?). Anyways, the Dr. Debug LCD does not show any persistent code once it starts so I am not sure what is happening since there is nothing from that diagnostic to go on. This has only started lately. When it first occurred I thought the power supply had finally given up and I went so far as to buy a brand new one and replace it...behavior is the same so I must assume there is some BIOS issue or perhaps some other hardware trouble that is causing it. Ironically I have changed absolutely nothing in the computer hardware wise except for the PSU, but the problem existed both before and after the PSU change, so I would think it is not that.
Any thoughts about what else I can look at or best tools to use to troubleshoot this issue?

Thanks,
~Dubhead

Hello,
   Thanks for indicating about the BIOS version. Did do the upgrade after totally clearing all BIOS values and unfortunately both of these things did not completely solve the issue. It is odd since I have disabled all other boot options except to boot to my M.2 SSD drive in the BIOS and it seems to work only on Fast (not Ultra Fast) and when I do a restart, it reverts all my settings back and re-enables my multiple SATA hard drives and USB connected drives and tries to boot to one of those. So strange that I save my BIOS settings yet it does not seem to respect them when I do the restart from Windows. Really at a loss as to why it may not like to persist with the BIOS settings when booting to the M.2 drive.

   Any one with any ideas about this? Maybe this older mobo doesn't really support booting from M.2 drives very well. Had thought I could at least use Ultra Fast boot also, but it never works.

Dubhead