Windows 10: Inexplicable restarts

I'd be very grateful for some expert help on the following please.

I run my PC 24/7. For the last two nights and again today it has restarted inexplicably.

I'm trying to discover what caused it. Studying Event logs quickly leaves me wondering how my PC can be working at all, and despair at ever finding the needle in the haystack. In Event Viewer I need to discover which of the daunting number of Warnings and Errors caused the restart. Many of them have apparently been occurring daily, so logically it seems I can rule those out.

Here are a selection of screenshots I'm hoping might offer
some clue. First for the overnight issues:

https://www.dropbox.com/s/0u7r9sthrz...ly-1.jpg?raw=1
https://www.dropbox.com/s/yrctcfl83i...ly-2.jpg?raw=1
https://www.dropbox.com/s/h308e1p2ir...ly-3.jpg?raw=1
https://www.dropbox.com/s/vzee1l8h20...2064.jpg?raw=1
https://www.dropbox.com/s/fb7wnz9ntc...0001.jpg?raw=1

And for the latest restart today, instead of Event Viewer, this time I downloaded and used Nirsoft's FullEventLogView. Here's a screenshot showing the entries around that time. (And, in case it's relevant, details of one of the many Event 504 entries.)
https://www.dropbox.com/s/v5ivxu868k...st-1.jpg?raw=1

Meanwhile I've just disabled Automatic Restart, so hopefully I'll get a clue next time it happens.

Also, in case it's a possible factor, I checked 'Update & Security' > 'Windows Update' and saw the reassuring
"You're up to date". But I clicked 'Check for Updates' anyway and there were two items. (One was 'pending..something or other' and the other a cumulative update, referencing KB4346783. I should have taken a screenshot.) So clearly I was NOT up to date. User error/misunderstanding, or a WU bug?

Terry, East Grinstead, UK

:)

 

Hard drive/ OS issue

a guy suggested :

• shutdown
• unhooked HDD
• restarted
• yay !!
• reconnected HDD
• restarted
• yay !!

also , try method 3
Fix: 'The Drive Where Windows is Installed is Locked'

 

random restarts

Hi Lili,

Hardware failure or system instability can cause the computer to
randomly restarts. As our initial troubleshooting step, we suggest you to run the Power troubleshooter on your computer and check if it fixes the issue. Here are the steps:

• Press Windows key.
• Type Troubleshoot.
• Under Find and fix other problems look for
  Power.
• Then Run the troubleshooter.

Update us with the outcome and if you need further assistance.

 

PC Randomly Restarting after installing new Ram!

Tried your suggestions, but still had a restart! Also ran memtest overnight (13 hours according to memtest) and had no errors! Also ran Passmark Burn in test for a couple hours testing everything and had no errors or restart. Could fitting the new ram have triggered something to go bad like my mobo or psu?