DIAGNOSIS This is typically a handshake issue between your graphics card and the monitor, often related to the cable, the refresh rate, or a feature like Adaptive Sync (FreeSync) acting up.
FIX Start with the cable. 1) Replace your current HDMI or DisplayPort cable with a certified high-speed cable. Cheap cables can't always handle the full data rate for high refresh rates and can drop signal. 2) Go into the monitor's OSD menu. Navigate to the 'Extra' or 'Gaming' menu and find 'FreeSync' (this monitor supports AMD FreeSync). Try turning it OFF. While FreeSync is great, imperfect implementation can sometimes cause brief black screens during frame rate fluctuations. 3) Also in the OSD, make sure 'Response Time' is not set to the highest setting (like 'Fastest'), as this can sometimes introduce artifacts and instability.
IF THAT DIDN'T WORK Update your graphics card drivers. Go to NVIDIA or AMD's website and download the latest drivers for your specific card. During installation, choose 'Custom Install' and check the box for a 'Clean Installation' to remove old settings. This resolves many compatibility hiccups.
HEADS UP If you're overclocking your GPU or using a heavily daisy-chained power cable setup for it, these black screens can be a sign of power instability. Try running your GPU at stock settings and ensure it's getting clean, dedicated power cables from your power supply.