What does it mean when your Apple Watch stays on with the Apple on the screen?
What does it mean when your Apple Watch stays frozen with the Apple icon on it
Apple Watch Series 3, watchOS 8
Question marked as
The white Apple logo is used as the startup splash screen when the Apple Watch is rebooting or loading a software update.
The most common cause is probably low battery charge, insufficient to let the watch reboot without losing power. If it has appeared without provocation the first thing I would try is put the watch on charge for an hour or so, then see if the watch has started normally.