Earlier today Apple released an update for watchOS and brings the version to 5.1. Users are usually encouraged to install software updates, they can provide new features, security, and other improvements, but you may want to stay away from this. We are seeing reports that watchOS 5.1 ticks some Apple clocks.
A single Twitter Search finds more users complaining that their watches were stuck on the Apple logo while they installed the 5.1 update and never restarted. There are similar reports on MacRumor Forums. Most complaints appear to come from owners of Series 4, but it may also affect other models.
Unfortunately, since you can not connect Apple Watch to iTunes to recover it, you're kind of just stuck. Some users have said that Apple sends them a replacement clock. At the time of publication, the problematic watchOS 5.1 update is still available, but again, we recommend avoiding installing the update until Apple resolves the issue.