To restart your Apple Watch, follow these steps:

1. Press and hold the side button until the power off slider appears.
2. Drag the Power Off slider to turn off the watch.
3. Once the watch is off, press and hold the side button again until you see the Apple logo to turn it back on.

If your Apple Watch is unresponsive or frozen and cannot be turned off normally, you can force restart it by:

1. Pressing and holding both the side button and the Digital Crown simultaneously for about 10 seconds.
2. Release both buttons when the Apple logo appears on the screen.
3. Wait for the watch to restart.

This force restart will not delete any data on your Apple Watch. It simply reloads the software to help resolve issues.