DIAGNOSIS This is a handshake failure between the GPU and monitor, often caused by cable issues, incorrect source settings, or power management.
FIX First, enable Input Signal Plus. In the monitor OSD, go to System > Input Signal Plus. Ensure it is set to 'On' for the DisplayPort input you are using. This disables the monitor's internal power saving checks that can interrupt signal.
IF THAT DIDN'T WORK Disable GPU power-saving features. In NVIDIA Control Panel, navigate to Manage 3D Settings > Power Management Mode and set it to 'Prefer Maximum Performance'. For AMD, in Adrenalin Software, set Power Saving to 'Off'.
HEADS UP The monitor's 'DisplayPort Version' setting in the OSD should be left on 'DP 1.2'. Manually setting it to 'DP 1.4' can cause instability with some GPU/driver combinations, even though the monitor supports it.