Why did my phone lock itself?

Most of the times this is happening when you have too many false passcode attempts. This can also happen when your iPhone tried to unlock itself in your pocket.

If you know your passcode, wait until the time out is over and enter your passcode. If you don't know your passcode or your iPhone is not accepting your passcode, you will need to erase your device. You will lose all of the data. on your iPhone which you have not backed up.

Follow these instructions in order to erase your device and remove the forgotten passcode

If you're using an eSIM, contact your carrier before trying these steps and ask for a QR code to set up your eSIM again.

1. From your device's Lock Screen, try to enter your passcode five times until the "[Device] Unavailable" screen appears and your device asks you to try again later.
2. When you're able to, continue to enter your passcode until the "Security Lockout" screen appears and you get the Erase [Device] option in the bottom corner of the screen.
3. Tap Erase [Device], then tap Erase [Device] again to confirm.
4. Enter your Apple ID password to sign out of your Apple ID on your device.
5. Tap Erase [Device] to permanently delete all of your data and settings.
6. When your device restarts, follow the onscreen instructions to set up your device again, restore your data and settings from a backup, and set a new passcode.

If you can't follow these steps, you can use a computer to reset your device.