Here are some steps you can take to stop your phone from constantly restarting:

1. Check your device’s memory to see if it is running low and free up some space.
2. Check to see if there are any apps or services that may be using too many resources and thus causing the device to overwork.
3. Ensure that your device is using the latest version of the operating system.
4. Check and change your power settings.
5. Ensure that your device is not overheating.
6. Reset your device to factory settings.