How to restart Samsung Mobile Device?
If the device is frozen and unresponsive, you may need to close apps or turn off the device, follow by turning on again.
To restart device, press and hold the Power key and the Volume down key simultaneously for more than 7 seconds to restart it.
Please note: This article is focusing on newer models such as Galaxy Note9, S9/S9+, Note8, S8, S8+, A8 and A8+, with the battery intacted within the device.
If the device remains frozen or unresponsive after restarting,, there are some actions that you can try to help correct this symptom:
• Shut down the device
• Press and hold the Power button. Release when Samsung logo appears and immediately press the Volume down button
Before performing the factory data reset, remember to backup all important data stored in the device