Mine does that too. I think it stops if you turn off HDR on the PS4.
Does the TV have local dimming? I unfortunately have to turn mine off (even though it looks great most of the time) on my Vizio because of random zones blooming when they shouldn't.
I've had this happen before! So I saw another post that said it was because the signal is getting goofed up and can't decipher if it's 4K HDR or 1080p Non HDR, so I did two things to fix this:
Once I messed with this setting, anytime it starts to flicker this generally fixes it
Try a new HDMI cord
PS4 and tv up to date? Also, game mode?
Yeah I know. I tried fifa 20 and it's was worse
The temporary solution that I found was to contact the Canadian Hisense support team, as US support team was not helpful, and request a link to downgrade my firmware in that should fix the issue of the flickering. The trade-off is that the downgrade will remove the Amazon prime app from the TV. However, I can access prime through my PS4 so I would rather have the flickering fixed.
Thank you all for your suggestions!
Is your auto brightness turned on?