My watch is completely dead no display and doesn’t respond to restart

The article If your Apple Watch won't charge or it won't turn on - Apple Support including the advice to Force Restart near the end of the article is the best resource for this situation. If you've completed that troubleshooting and the issue is still not resolved, use the link in the article to Contact Support. Or Genius Bar Reservation and Apple Support Options - Apple

Try and force restart your iPhone to see if the problem persists

You should force restart your Apple Watch as a last resort and only if it's not responding.

Don’t force restart your Apple Watch if you're updating watchOS. After you see the Apple logo and progress wheel, leave your watch alone and on its charger until the update finishes.

To force restart your Apple Watch, press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo.