Monitor keeps blinking off for a few seconds then comes back

first thing to rule out is the cable. if it's HDMI or DP and it blanks for a couple of seconds then comes back, that's usually the signal dropping and the monitor re-syncing. swap the cable before anything else, cheap ones are the usual cause at high refresh rates. if a new cable doesn't fix it, try dropping the refresh rate one step and turning off adaptive sync / g-sync compatible for a day. if it stops, it's the panel not liking that mode. a clean driver reinstall is the last step.