my Apple Watch is asking for a email but I don't know it
how to connect my Apple Watch to my phone but asking for a email
That watch is likely under Activation Lock. Which means that it may have been lost or stolen.
Activation Lock prevents lost & stolen watches from being used by anyone but the owner.
Only the owner can remove the Activation Lock.
M1 Mac mini, macOS 12.0.1; Watch, series 5 GPS/cellular, watchOS 8.1; iPad Pro 2nd Gen, iPadOS 15.1; iPad Air 2, iPadOS 15.1; iPhone 12 Pro, iOS 15.1; TV 4th Gen, tvOS 15.1; HomePods, audioOS 15.1 and Airport Express w/ Airplay 2