Reboot issues may be classified as the following,

Reboot in standby: The device suddenly restart while standby.

1. If the issue appears occasionally, it may be caused by anomalies in a file, it is recommended to observe the use.

2. If the issue appears often, check if the handset has already root not, if yes, please back up all the data, clear cache and flash to the latest OS version.

3. Check whether too many Apps running in the background that occupied too much hardware resource.

4. Make sure to Enter into"Setting"--"Utilities"--"Scheduled power on/off" is disabled.

Reboot in third-party Apps

Please confirm if the issue occurs in one third-party App or other third-party Apps too,

1. If the issue occurs in one third-party App, please uninstall the third-party App, clear cache and check the latest update.

2. If the issue occurs with other third-party Apps, make sure the app is compatible with the latest Android version. Try uninstalling the third-party Apps, please clear cache, back up all the data and flash back to the official latest OS version. Enter into"Setting"--"Utilities"--"Scheduled power on/off" to check if it is disabled.

Reboot in preload Apps

Please back up all the data, clear phone's cache, then restore the factory setting or flash to the official latest OS version.