iPhone keeps restarting itself every 3 minutes

Solution 1:

Since using iTunes to restore the iPhone can't solve this problem, the following method is worth a try:

  1. Restore all settings on your iPhone.
  2. Update all applications or remove potentially conflicting applications
  3. Remove the SIM card from the iPhone and check if it stops restarting
  4. Check and clean the charging port
  5. If you restart when charging, please replace the iPhone battery Finally, it is recommended to contact Apple officials for the best solution.

https://www.fonecope.com/fix-iphone-keeps-restarting.html