I got the same Problem, my solution was to disable doze_always_on.
You can check if its on with
adb shell settings get secure doze_always_on
and to disable
adb shell settings put secure doze_always_on 0
I too did a restore from a backup (Pixel 3). I could not believe there is no other solution other than a factory reset so I invested some time. 
PS: or you could use the App
and disable “Ambient Display”
Hope this helps!
greez n3utrino