Question Why does the system reboot if I don't Enter Bios in 5 sec or less?

[sreilly24590]

My observatory computer ran into some issue weeks ago. It was a Windows 7 64 bit system and started rebooting several times daily. I knew it had rebooted as the startup programs were running as normla but Dashlane was not signed into. I have since converted a Windows 10 64 bit system to operate it in the meantime but world like to repair this system.

The MB is a Gigabyte Z170X-Gaming 7. The system is stripped down to just the DVD and SSD. Had 32GB RAM that was listed on the G Skill site as compatible and worked for several years prior without issue. The computer now boots as far as BIOS screen and if I don't hit the Del key within 5 seconds it reboots again and again. I can enter BIOS and have tried setting to the optimized defaults and still have this issue.

I have switched out the CPU and memory, each one at a time and tried with same results. I do suspect the SSD has boot issue but I don't even get past setup. After BIOS changes it repeats the same behavior of restarting itself if you don't enter setup. There no cards installed on the MB, using the HDMI display to the monitor which does work, keyboard is a SP2 connection, mouse USB.

The BIOS was updated to F22 several weeks ago after issue started, prior to that it was f16 I believe.

Specs:
Gigabyte Z170X-Gaming 7 Ver. 1.0
Intel i7-6700k CPU
G Skill F4-2133-C15D-32GVR or F4-2400C15D-16GVR
CPU Temp 36C
DVD is connected on SATA 0
SSD is on SATA 1 Samsung 1TB MZ-75E1T0B/AM
PSU is Antec 650 watt 80+ new

Any ideas? It's a continuous cycle of restarts if you don't enter the BIOS setup within 4-5 seconds, simply reboots and goes on and on....Changing settings makes no difference to this behavior. The digital display shows A2 before entering setup if Del is hit.

 

[sreilly24590]

It occurred to me that after a few days of the system rebooting itself when it was operating somewhat normally I updated the BIOS to F22 which is where the ability to boot ceased and this new behavior started. So I decided yesterday to use the QFlash function of the MB and flash the BIOS to a lower version, in this case F21, which actually allowed the system to boot normally.

So now I'm back where I started and have the system running 24/7 and after 9 hours at least it did reboot sometime after midnight. So where can I look to see if Windows 7 has any record of this reboot as it wasn't done by choice. Evidently something happened to cause the reboot.

I've taken all the astronomy observatory software out of the Start Menu so it starts without these cause other issues as nothing is connected at this point. I did however put a shortcut to Notepad so I have some sign that a reboot has occurred.

Any suggestions on how to trace the time and cause?