The One M8 is a smartphone released by HTC that runs on either Android or Windows. It includes an optional fastboot feature that enables you to turn on the phone more quickly than when it is not activated. Normally, fastboot mode is a convenience. However, as it stops the phone from ever fully powering down while enabled, it is not ideal for performing troubleshooting and repairs.
This FAQ will show you how to disable the fastboot feature on your HTC One M8.