Xbox keeps turning off in less than 5 minutes whenever I turn it on

Sorry to hear it. Is this the original Xbox One with the external power brick? If so then I'm afraid that Xbox no longer supports those consoles for repair.

However, you could check your local gaming store for a new brick to see if that was the problem

Same issue here. Switches to 7.1 whenever I turn off the Xbox for more than a few minutes.

Sometimes, the console is downloading certain information or doing other tasks. But I assure you that the console will turn off in less than 5 minutes. (Only if you're downloading something or you are charging your control the console will continue turned
on)

Regards!

Whenever I do that, my xbox turns off in 5 seconds

I've found that if you press and hold the sync buttons on both the console and the new controller at the same time and for 5 seconds, it will sync up in less than a minute.. Make sure the controller that came with the console is turned off as it helped in
the sync process.