Not sure if this has been solved, but I had the same issue on my qfn55, got a service tech around and they replaced the input cable that runs from the TV to the i input box and it solved the issue.
i have the same issue with my qled q8fn55. bought it february and everthing was fine till two months ago. my xbox one x and ps4 pro both have tv restart during gameplay. i have factory reset the tv, deleted xbox in universal remote, got a new samsung tv remote, turned off hdmiec, turned off mobile device turn on, etc. anything i can do to fix it i have tried twice with no luck.
The consensus with your TV is a bad One Connect cable.
The work around for everyone if you still have the problem is turn off freesync.
Why buy a TV that advertised freesync and not be able to use it?
My personal feeling is Samsung don’t care.
They have your money.
The only common thing with all the models affected, is the firmware, it is the same and some have issues with Xbox one X. Others have worked around it by turning off Freesync.
But Freesync is why most bought the TVs.
Here is some links related to this prolem posted elsewhere.
I am sure that if you do more searches for this problem on youtube you will find some.
Matches my problem with Q6FN QLED TV's (Firmware is the same from NU7400-NU9000-Q6F-Q9F) https://eu.community.samsung.com/t5/TV/55-Q6FN-Reboot-Only-With-Xbox-One-X/m-p/1205112#M27699
Q9FN having issues with Xbox One X restarting (Q7-Q9 QLED TV have a One connect Box) https://eu.community.samsung.com/t5/TV/Q9FN-random-reboot/td-p/1163027 https://eu.community.samsung.com/t5/TV/Q9FN-random-reboot/m-p/1163027#M26986
NU8000 having issues with Xbox One X restarting https://www.reddit.com/r/4kTV/comments/9z3je1/samsung_nu8000_constantly_rebooting_with_xbox_one/
Q6-Q9 having issues with restarting some have issues with Xbox One X restarting (most have solved it with a different optical cable to One connect box) https://us.community.samsung.com/t5/Qled-and-Frame/Samsung-QLED-TV-Turning-Off-and-On-by-itself-remo...
You stated the TV restarts when connected to the Xbox OneX and the PS4. Are there any other devices that cause the TV to restart?
my tv does not have a one connect box. so that cannot be the issue. not about to turn off free sync and not use the features i paid 1500 for. would rather buy a new tv. i dont have any other devices plugged into it besides xbox one and ps4. no home theater system or soundbars or anything
That is the problem when it comes with hardware that needs software to run, because software is human built and hardware don't know a glitch when someone makes a mistake trying to make somthing else better and in time this will be fixed.
Trust me techs are paying attention to us the consumers and heck they use the products too, so just try to find a solution to get around this until there is another firmware fix.
Best regards a samsung customer.