You will need to
force your  Apple device  to restart if it continues to freeze and lock
up after you have shut it down and turned it back on. The  hard reset of an Apple
Watch  is also called this.  

You can do this in a few seconds using this simple method.
Please keep in mind that this will not affect the data on your  apple watch .
The  Apple watch device  is simply restarted.  

Note:  A charging  Apple
watch  cannot be restarted, so you must
unlock it before proceeding with the following steps. Read the full blog
here: https://www.soldrit.com/blog/how-to-force-restart-or-hard-reset-apple-watch/