iPhone XS black screen with corner lit up and time dim

Occasionally I wake up in the morning and my iPhone Xs with IOS v. 18.1.1 has a strange black screen, but with the four corner icons lit up (camera, flashlight, wi-fi, and signal/battery strength). The lock icon is lit too, and the time is super dim almost unreadable.

If I tap the screen, it goes totally black (off). If I tap it again, it wakes up normally. My lock screen is an ordinary daylight photo.

This doesn't cause me any problem, just seems very strange and suspicious.

[Re-Titled by Moderator]