[Galaxy S8/S8+] How to restart the device if it hangs?

If your device is frozen and unresponsive, you may need to close apps or turn off the device and turn it on again. If your device is frozen and unresponsive, press and hold the Power key and
the Volume down key simultaneously for more than 7 seconds to restart it.

If after restarting the device you still find your device freezes sometimes or is sometimes
unresponsive, there are some actions you can try to help correct this symptom:

1. Use the Galaxy S8/S8+ Device maintenance menu to help optimize the device and check for
“Malware”. (SMART Manager may not be available depending on the region or service provider)

2. Create memory space

3. Check for SW updates for your device

4. Check your device in “Safe mode”

5. Perform a Factory data reset of the device.  Before performing the factory data reset,
remember to make backup copies of all important data stored in the device.

      If the problem is still not resolved, contact a Samsung Service Centre.