Xbox turning itself off / reset will not complete

have you tried turning the console off completely then back on again,it may just need to reset itself.

Is the Xbox turning off completely or constatly restarting itself?

Or other than sending it in for repair you coul try visually resetting it, if there is a disc in the tray remove it, then turn off the 360 and allow it to completely shut down, once it's off use your 360 controller to turn it on, when the system turns on
immediately press the right trigger and the y button and hold them throughout the Xbox logo loading screen, the system will then reset itself and the display settings will be reset

If you use the "instant on" mode on your One, have you tried a hard reset? Turn your console off via the console itself and hold your finger on the button for about 10 seconds until the console turns completely off and the light on the PSU turns orange,
then turn it back on.

That issue usually resolves itself, however, I’ve fixed it by resetting my console by holding the power button on the console for a full 10 seconds until it turns completely off. Wait 30 seconds then turn it back on and try again.