Computer Restarts By Itself

I've noticed this on several new Dells that I've worked on recently.  Generally they've been of the XPS variety but at the moment it's a couple of Vostro 5880s.  i7 processors, 32GB of RAM and SSD storage.  In every case I've done a bare-metal re-install of the OEM version of Windows 10 Pro (bought with the computer), upgraded to the latest release.  Nothing is set in the BIOS to tell it to restart under any circumstances (timer, NIC, etc) and I've made sure that "Automatically restart" is not enabled under Windows Startup & Recovery as well.  No unique programs have been installed, just Office 2019 Home & Business.  I happened to be on a call with Dell ProSupport today about another issue and I mentioned it to the tech kind of as an aside.  She said there have been occasional reports of a problem and that "seemingly" having the Wi-Fi chip enabled at the same time as the NIC has been know to cause such a problem.  Now that just happens to be my exact situation; I use a hardwire network connection but keep the Wi-Fi enabled just in case (for whatever weird reason) a cable problem develops and it needs to switch-over to a Wi-Fi connection.  I shut Windows down normally (via the Start button) but within anywhere from 3 to 5 minutes later it just mysteriously boots itself back up.  I've had to pull the power cord to keep it from rebooting on its own.  I never would've imagined such a thing but it's as good a guess as any, given that I've seen this exact same scenario play-out multiple times in the past, as well as currently.  It would definitely be what I'd call a bug. Sure, the Wi-Fi can be disabled easily enough but should it have to be, just because you're using a hardwired patch cable connection?  Any input is welcomed...