Hi Peaches1975,
We understand that your Apple Watch is restarting after trying to update it, and we want to help.
Based on the error you're seeing, it's possible that the issue may be hardware related, but we want to do everything we can to help narrow this issue down.
Just confirm, when you tried to update, did you see any additional error messages saying something like "Unable to Install Update"? If so, the steps on this page may help: If you see "Unable to install update" when trying to update Apple Watch Series 1 or Series 2
Which iOS version is your Apple Watch's paired iPhone running at this time? Find the software version on your iPhone, iPad, or iPod
Also, just to make sure we're on the same page, can you let us know if your Apple Watch displays anything on the screen when it restarts now? For example, does it show the Apple logo, or something else?
Thanks!