Hi Gordon. I'm Greg, an eleven years awarded MVP, Volunteer Moderator, and Independent Advisor here to help you until this is resolved.
1) See fixes for random screen locking:
https://superuser.com/questions/1017626/why-doe...
https://www.thewindowsclub.com/stop-computer-fr...
https://www.askvg.com/fix-lock-screen-appears-a...
https://answers.microsoft.com/en-us/windows/for...
https://www.tenforums.com/general-support/38337...
https://answers.microsoft.com/en-us/windows/for...
https://social.technet.microsoft.com/Forums/en-...
https://forums.tomshardware.com/threads/windows...
https://www.youtube.com/watch?v=BIex2RmMEHE
2) Go over this checklist to make sure the install is set up correctly, optimized for best performance, and any needed repairs get done:
http://answers.microsoft.com/en-us/windows/wiki...
Start with Step 4 to turn off Startup freeloaders which can conflict and cause issues, then Step 7 to check for infection the most thorough way, then step 10 to check for damaged System Files, and also Step 16 to test a new Local Admin account. Then if necessary continue with the other steps to go over your install most thoroughly.
3) Update your drivers and BIOS/UEFI firmware from PC or motherboard maker's Support Downloads web page, using the full model number, Serial Number or Dell Service Tag on sticker. Compare the latest drivers available for download with the ones presently installed in Device Manager reached by right clicking the Start button. Make sure you have the latest BIOS or UEFI firmware, Chipset, Display (Video), Sound, USB3, Bluetooth, Network and all other drivers, or else download and install the latest now.
Updating drivers from the Device Manager or Windows Update is rarely enough. The most basic thing we need to learn to maintain a PC is keep the latest manufacturer's drivers installed from their Support Downloads web page.
4) If nothing else works then do a Repair Install, by installing Media Creation Tool, open tool and choose to Upgrade Now. This reinstalls Windows while keeping files, programs and most settings in place, is the most stable method to advance to the latest version, and solves most problems.
http://windows.microsoft.com/en-us/windows-10/m...
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But remember that in Windows 10 everything depends upon the quality of the install, and Factory or Upgrade installs are inferior installs which most enthusiasts won't even run because they'd expect endless issues. Consider now or later doing the Clean Install in this link which compiles the best possible install that will stay that way as long as you stick with the tools and methods given:
http://answers.microsoft.com/en-us/windows/wiki...
There is also an automated Fresh Start that reinstalls WIndows while shedding corrupting factory bloatware, saves your files, but doesn't clear the drive to get it cleanest:
https://www.howtogeek.com/265054/how-to-easily-...
I hope this helps. Feel free to ask back any questions and let us know how it goes. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.
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