It keeps vibrating and making a ding noise whilst it vibrates when it's on sound mode and it doesn't go away if it's on silent I've tried emergency alerts accessibility settings looking at potential apps and I've looked at maybe if it was a virus but it seems like it's none of those issues
You have probably got a credit card near your phone so every time you unlock your screen, the NFC is trying to read the card. This also started happening to me recently. So I reckon it is due to a recent update as I never had this issue in the past.