If you receive a notification on your iPhone Lock Screen that an unknown AirTag is moving with you, here’s what to do! You’ll receive a notification as long as you have Location Services and Bluetooth turned on. Go to “Settings and tracking notifications”, and then turned on in “Notifications”. If you receive a notification that says, “AirTag Found Moving With You”, tap the alert, then tap “Continue”.
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“Find My” displays a map with red dots and dash lines, where the AirTag was detected near your device, and the approximate sequence where it was detected. Red dots don’t indicate if the owner of the AirTag was viewing its location. Tap “Play Sound”, then listen for the sound.
You can play it again if you need more time to find the AirTag. Once you locate the AirTag, swipe up on the item card on your iPhone to see more options. If you know who this AirTag belongs to, you can tap “Pause Safety Alerts” to stop receiving alerts. If you aren’t familiar with this AirTag, you can tap “Learn About This AirTag”, then follow the onscreen instructions. To disable this AirTag so it can no longer track you, tap “Instructions to Disable AirTag” and follow the onscreen instructions. And that’s how you locate an AirTag moving with you.
Source:How to locate an unknown AirTag moving with you on iPhone | Apple Support