I have 55Q6FN and Xbox One X and I have exactly this issue (Reboot, Samsung logo,remote control sensor led blinking and "samsung account is connected".
I'm checking with Freesync DISABLED and and it seems to be no problem so I think the problem is freesynch.
But this is very big issue, because with this panel some games (example Fifa 19) suck without freesync, trails on screen everywhere...
I have 12.51 firmware, I have not updated to the latest version 1260.8 because I read that it really sucks.
Has anyone tried the version 1260.8?
"Customer Support says 1260.8 is “an offline Update” and is only available via USB download."
Absurd samsung support, the 1260.8 is online, I also received the notification today from the TV ... No more samsung, did the phones that the TVs are not for them.