Why Does My iPhone Keep Saying Passcode Is Required To Enable Face ID randomly when unlocking the phone

Yesterday, I received the replacement of 16 PM after a hardware issue on previous device and ran into an odd case.The first time this happened to me was in the morning when I tried to unlock my phone using Face ID, but instead I got the message, "Your passcode is required to enable Face ID." At first, I thought it might be an extra security feature, but today, when I used my phone for a while, put it aside, and picked it up after ten or fifteen minutes, the same message appeared again.

Since the first item I received had a hardware problem, this one is already a replacement.At the same time, I'm inquisitive and concerned about what the devil is going on. Has anyone among you experienced this?If you have experienced this or something similar, do share your experiences with me.Additionally, I spoke with Apple support over the phone, and they performed a diagnostic. Everything appeared to be in order, but my device is now at 18.1.1 and has not yet been updated to 18.2.1. I will update it and double-check.