Have you tried turning off Adaptive Brightness? You can go to Settings > Display and tap the switch off to Adaptive Brightness. If that didn't solve your issue, you might need to boot into Safe Mode and check if the flickering still persists? This might be an app issue on your end.
Hope this quick fix can help you with your issue. Thanks!
I'm so sorry for this, itsleramickey. You need to go to an Authorized Samsung Service Center for a check-up and consultation. You can find the nearest Samsung Service Center in your area here: https://www.samsung.com/ph/support/service-center/?msclkid=72d47e20cf8411ec8ac1394658c823b0
You can also contact our customer support if you can't access the Service Locator website. Here are our contact details:
Mobile Devices Hotline:
#GALAXY (just dial #425299) [Toll Free to all networks]
(02) 8422-2177 [Standard Landline]