My iPhone keeps restarting by itself

Thank you for your reply.

I'm sorry if it's not helpful for you, if you checked the update of your device and it didn't work and checked the battery of the device and found that it doesn't need to be changed and your phone continues restarted itself, you'll have to contact Apple Support

Hello there!

Please follow the steps in the following link for support with this issue: If your iOS device restarts or displays the Apple logo or a spinning gear unexpectedly