Safe Mode puts your phone in a diagnostic state (returned to default settings) so you can determine if a third-party app is causing your device to freeze, reset or run slow.
An alternate method is available if the device can be powered on and is responsive.
With the device powered off, press and hold the Power button for approximately 3 seconds then release.
After the device vibrates (approximately 4-5 seconds after the Motorola logo appears on-screen), press and hold the Volume down button.
If the button is pressed prior to the device vibrating, it will not boot into safe mode.
Continue to hold the Volume down button until Safe mode appears in the lower-left of the unlock or home screen then release.
This may take up to 30 seconds.