Why is my Series S stuck In the startup screen and then it turns off and turns on normally?

With issues like these, we recommend trying some basic troubleshooting steps such as the ones listed below. It will help freeing some space on your console and prevent any further issues from occurring.

Clear Mac address: Settings > Network Settings > Advanced Settings > Alternate Mac Address > Clear it and the console should restart. It would definitely help if you could restart the internet router while the console is restarting.

Close any running games: To remove download constraints from games or apps being installed, you can either wait for the Xbox to suspend the running game, or you can force games to close by doing the following:

1. On the Home screen, navigate to your most recently run game.
   
2. With the game highlighted, press the Menu button and select Quit.
   

Reset your console: If you are still encountering the same issue, please select System > Settings > System > Console info > Select Reset console > Choose Reset and keep my games and apps.

Note =>The "Reset and Keep my Games and Apps" option will not cause losing your games, but please be aware that you need to be completely aware of the email address as well as the password of your account before going for it because it will require you to sign in to the account.

Also ,If it happens again and you get stuck, you might want to try the steps listed here: Troubleshoot system updates on Xbox | Xbox Support

had the same problem with my 360 s. i turn it off and sometimes it takes 10 to 15 seconds to turn off. other times it goes back to the startup screen without turning off and back to the dashboard. rather frustrating when it happens.

got the same issue with my xbox series s, i was watching netflix and then the screen turned black, tried to turn off the console but nothin worked

Yes I did why would my one s work and the series x not work??? Why did it turn it off once and not again? Turns it on just fine!

The power button on my Xbox started flashing when it got to the startup screen after that the screen turned black and it booted up normally