• Your phone reboots or powers down.
• Your phone turns off while in use.

It is important to make sure the issue is not related to the screen timeout settings. This can be done by pressing the POWER button once after the issue occurs. If the phone screen immediately shows the same screen as before the issue occurred or the lock screen, the phone is not powering off or rebooting.

Verify that the phone is not powering off due to the battery not having enough charge, by following these steps:

1. Once the phone powers on, check the battery level when the issue occurs.
2. If the battery is very low when the issue occurs, ensure you are charging your phone enough.

Updating your phone software may also resolve the issue. Ensure the phone is fully updated, by following these steps:

1. Navigate to Settings > System Updates. The exact path will differ depending on your phone.
   These are the three typical paths:
   
   Settings > System updates > HTC software update
   Settings > Software update
   Settings > AT&T Software Update
   
   
2. Select HTC Software Update to check for new updates.
   If an update is available, follow the on-screen prompts to download and install the update.
   If no update is found, confirm the device is on the latest software version by navigating to Settings > About > Software Information.

NOTE: If the phone is not on the latest software versions and updates are not found when performing the above steps, the update will need to be installed using an RUU for the phone. See ROM Downloads For Your HTC Smartphone for detailed instructions.

Sometimes the issue may be caused by issues with an application. See My apps are not working.

Some developer settings can also cause the phone software to become unstable, which may result in the phone rebooting. Follow these steps to turn off developer options:

1. Navigate to Settings > Developer Options
   If this option is not available, you have not enabled any developer options.
2. Turn Off the options using the slider in the upper right corner.

A factory data reset can also resolve some software issues. See How to factory reset a device.