Diagnosis
This is a failure in the monitor's wake-from-sleep signal detection. The main board isn't properly recognizing the active signal from the GPU after a system sleep.
How to Fix It
Disable Windows Fast Startup. Go to Power Options > Choose what the power buttons do > Change settings that are currently unavailable > uncheck 'Turn on fast startup'. Next, in the monitor's OSD, go to System -> Auto Source Switch+ and set it to 'Off'. Also, set 'Auto Off Timer' to 'Off'.
If That Didn't Work
Update your GPU drivers. Then, in Windows, go to Device Manager, find your monitor under 'Monitors', right-click, select 'Properties', go to the 'Power Management' tab, and uncheck 'Allow the computer to turn off this device to save power'.
Heads Up
This is a common firmware-related bug. Check Samsung's support site for a firmware update for your model. Updates often address sleep/wake compatibility.