If your phone is stuck in a loop of continuously restarting, try these steps to resolve the issue:

1. Confirm your phone is charged, or connect it to an external power source.
2. Try restarting your phone.
3. Check to see if your phone's software is up to date.
4. Reset the phone to factory settings and restore your data.
5. If the above steps do not work, take your device to a telephone technician or manufacturer for assistance.