Kick the iPhone X awake when the screen freezes.

1. Press volume up.
2. Press volume down.
3. Press the power button on the right side of the device opposite the two volume buttons on the left edge.

To keep the phone from freezing to begin with it might be best to power it down and then up at least once a week. Do that by holding the power button and the volume up button together. This act will both power down and power up the phone. You need to take a break between the two actions. Do not except the phone to power down and then back up again while you consistently squeeze it.