Question marked as
Try rebooting your phone:
Press and quickly release the volume up botton
Press and quickly release the volume down button
Press and keep holding the power button (keep holding past Swipe to Shut Down) until the Apple Logo Appears
Your phone will restart. If this problem persists after this, schedule an appointment at your Apple Store Genius Bar for evaluation.
Is your phone in a case by any chance? Could that case be interfering with the Ture Depth Camera? To test, take your phone out of the case and see if that's the issue.