xbox one wont startup. it flashes once then shuts off. I have tried unpugging console etc...

The light flashes when the console is downloading content from Xbox LIVE. If the console is in the middle of downloading something and you shut off the console, it will still finish the download. If you want the console to shut off without finishing downloading
content you can turn off background downloads. Navigate to Settings > System Settings > Console Settings > Startup and Shutdown > Background Downloads and click "Disable". Hope this helps!

Set your xbox one's power mode to energy saving instead of the default instant on and it will allow the system to fully shut down when you turn off the system instead of staying in a standby based off state. This will let the ram boot up clean and wont
have this issue. You can reenable instant on mode once you reboot with energy saving mode. But ive found it best to atleast turn off ur xbox with energy saving on atleast once a week to let it do a full startup.

Hey Vlad,

Thank you for reaching out. From the information you provided, it seems your console tries to startup, but immediately shuts off and produces some sort of sound while doing so. If you haven't already done so, go ahead and check out our

Console Shuts Off and
Power Supply Troubleshooting articles. These should let you know if a
repair would be needed for your Xbox. Hope this helps!

Checking in. Day 2 my brand new xbox one S still wont make it past step 3 of the startup. Once it tries to update i get the error code...

Hey there Tavan,

Sorry to hear you are running into this problem. I would advise going through the "Troubleshoot Xbox One startup errors" support article. As stated,
If the Reset did not work you will have to try to
Reset your Xbox One console to factory defaults using a USB flash drive.

Once you go through those, if you are still running into this problem then the console would need to be serviced.

I hope this helps.