Sigh! This issue has been around for years. I haven't got a fix, but there is a workaround: disable Monitor Sleep in Windows 10 Settings.
This message was posted on behalf of Intel Corporation
Thank you very much for taking the time to reach the Intel® Communities Team.
I understand you are facing some issues with your NUC which will not reactivate after going to sleep mode with 4k resolution.
I would highly recommend you to update the Graphics Drivers. You can download the latest drivers by clicking here.
Then, in order to complete the installation please follow these steps:
1. Start Control Panel, click Hardware and Sound, and then click Device Manager.
2. Expand "Display Adapter", right-click the Intel Graphics entry, and click Uninstall.
3. On Confirm Device Removal dialog box, click Delete the driver software for this device option to delete the Intel HD Graphics driver then click OK to start the uninstall process.
4. When the uninstall process is complete, disconnect your computer from the internet and make sure it will not auto connect when reboot. Restart your system.
5. Unzip the file to a designated location or folder.
6. Open Device Manager
7. Expand the Display adapters section.
8. Right-click the Intel® graphics entry and select Update Driver Software. (Note: The graphics entry may be "Microsoft Basic Display Adapter")
9. Click Browse my computer for driver software.
10. Click Browse and select the directory where the driver files are found.
11. Click Next. Drivers are now being installed.
12. Reboot your computer when prompted.
Please let me know the results.