I have the same problem and it is really annoying (latest ios14 iphone se 2).
The first update made it better for days but now it is the same. I think the apple made it like it would have a faceID, but it doesn’t. With faceID phones you have a setup which is awareness something. If you are looking towards the phone it gets down the alarm sound. If you do not face it, it goes back. It works like that with my phone, but we cannot set it off because we do not have that option.
I don’t get the calls and messages i should so it feels like I have an old school phone, not a new expensive one.