Update your Apple watchOS
Many issues are caused due to outdated firmware and bugs, hence it is always a best practice to keep your iOS and watchOS updated as soon new update rolls in. This is how you can update your watchOS:
Step 1: keep Apple watch connected to charger
Step 2: On your iPhone, go to Apple Watch app
Step 3: Tap on "My Watch" tab inside the application
Now tap, "General> Software Update", download the update and wait till the process is completed.
Restart Apple Watch
Step 1: Open "Settings" app on your Apple Watch
Step 2: Navigate to "General>Reset>Reset All Content and Settings"
Step 3: It will prompt for passcode if any and at last confirm selection to reset your Apple Watch
Wait for the process to end, your Apple Watch will be just like it was new.