Hi CD. I'm Greg, an installation specialist, 10 years awarded Windows MVP, and Volunteer Moderator, here to help you.
I will give you everything I've compiled that works to troubleshoot Sleep over the past ten years in thousands of cases in forums. Evern if you've tried a step please try it over in sequence as one of these almost always works.
First confirm you have the Sleep options configured correctly as shown here:
https://www.tenforums.com/tutorials/2843-change....
Most Sleep problems are caused by the Display driver, so try updating yours from the PC or Device maker's Support Downloads web page for your full model number, Serial Number or Dell Service tag. While there make sure you have the latest BIOS, Chipset, Network, Sound, USB and all other drivers by comparing those posted for download with the version and date of the corresponding ones in the Device Manager.
If that doesn't help then in Device Manager on Display device Driver tab choose Roll back, Uninstall (then restart to reinstall) or try another one previously installed at Device Manager>Display adapter>Driver>Update Driver>Browse>Let me pick.
In addition there are steps here to specifically troubleshoot Sleep mode problems: http://www.makeuseof.com/tag/fix-windows-10-sle...
https://www.vistax64.com/threads/power-options-...
https://www.howtogeek.com/122954/how-to-prevent...
What I do is go into Advanced Power options and set Display and Sleep to 1 minutes, Hibernate to 2 minutes, then after completing each step restart the PC and observe what happens for 3 minutes.
You might want to try Hibernate to succeed Sleep, or use Hibernate in place of Sleep - it's a deeper sleep that actually powers off because the session stored in RAM during sleep is written to hard drive hiberfile then powered off. When it starts up it loads the hiberfile and starts faster.
To Troubleshoot Hibernate:
https://pureinfotech.com/fix-hibernate-problems...
This may have been caused by Windows Updates. Check which Updates were installed right before the problem began, and if necessary uninstall them from Settings > Update & Security > Windows Update > Installed Update History.
You can also try to roll back using System Restore to a point before this began:
https://www.windowscentral.com/how-use-system-r...
Then if an Update reinstalls and causes the same problem uninstall or roll it back again, then immediately hide it using the Hide Updates tool from Method Two here:
https://www.howtogeek.com/223864/how-to-uninsta...
If nothing else helps you can run a Repair Install by installing the Media Creation Tool and choosing from it to Upgrade Now. This reinstalls Windows in about an hour while saving your files, apps and most settings, solves many problems while also bringing it up to the latest version 1903 which you need anyway and by the most stable method. http://windows.microsoft.com/en-us/windows-10/m....
I hope this helps. Feel free to ask back any questions and keep me posted. 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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