I managed to trace one of the unexpected shutdowns from the System Event Log.
Log Name: System
Event ID: 6008
User Name: N/A
The previous system shutdown at 2:38:08 AM on ?12/?30/?2017 was unexpected.
Unfortunately, there isn't much helpful information apart from that. On the other hand, I do suspect that the problem isn't an actual fault in Windows — it's a fault with the BIOS. Your BIOS version is over a year old, version 1.9.4, according to SystemInfo:
BIOS Version: Dell Inc. 1.9.4, 11/4/2016
Now there appears to be a bug in version 1.9.4 (perhaps before that) which was patched in December of last year with version 1.9.5, and it sounds very close to your problem. I am quoting from DELL's support page for version 1.9.5:
- Fixed system restart issue when both Device Guard and Credential Guard enabled in Win10 enterprise.
- Fixed system only can switch display to external monitor one time by lid close in the Bios Setup.
- Fixed system become reboot from hibernation resume after loading Bios default. [sic]
Hence I would update your BIOS to the latest version — that is, version 1.15.4. I would suggest you double-check whether what I'm seeing is what you're seeing, i.e., that the BIOS update linked is truly applicable to your model. And of course follow all of DELL's precautions.
Edited by bwv848, 30 December 2017 - 05:46 PM.