Why my computer restarted without notice? [40 minutes of silence without trail]

Why my computer restarted ?

Yesterday left my computer unattended for a couple of hours, as I come back, computer was restarted losing some of the things I didn't save (some temporal notes, some incognito windows), nothing valuable, but uncomfortable. Restarting neither reopen my explorer windows (neither really important, but it is nice to have your working folders opened.)

Looking trough logs, I can NOT find a reason for that, and this is what brothers me.

Control Panel\System and Security\Action Center\Archived Messages return no message at all

while Control Panel\System and Security\Action Center >> Maintenace sais that "one or more devices connected to your PC needs additional software to work properly", when I had not change any physical thing on my PC

On Event viewer. Summary, I had the following message: The previous system shutdown at 17:25:26 was unexpected. at 18:06 !!!!

• that means the computer was 41 minutes since shutdown to be back again ??

From this period of time (around 17:25 to 18:06) I had the following message:

Warning     17:27:21     Security-SPP
    The rules engine reported a failed VL activation attempt.
    Reason:0x80004001
    AppId = 0ff1ce15-a989-479d-af46-f275c6370663, SkuId = b322da9c-a2e2-4058-9e4e-f59a6970bd69
    Trigger=TimerEvent

after this event, also Security-SSP, 30 seconds later, two informational messages:

    Successfully scheduled Software Protection service for re-start at 2019-06-17T17:26:51Z. Reason: RulesEngine.

    The Software Protection service has stopped.

    ..then silence...

until sysems seems to be back again

Critical    18:06:02     Kernel-Power
    The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.

and really nothing more, I can't see any other information or log that gives me a clue about it.

and second thing that brothers me, as I try to make a custom View on EventViewer, It fails with the next message:

FX:{b05566ad-fe9c-4363-be05-7a4cbb7cb510}
The process cannot access the file 'C:\ProgramData\Microsoft\Event Viewer\Views\View_0.xml' because it is being used by another process.

I check the file, it has been created (with about 100kb, an XML with the filter defnition), and with ProcessExplorer I see no handler pointing to this file.

May somebody give me a bit of light ?

Neither seems to be related to winodws update, last one in history was 5 days ago.

My system: Windows 8.1 running in a Laptop Lenovo with 8gb and SSD