Xbox one S ventilation

Both the Xbox One S and the original Xbox One consoles are designed to ventilate air to keep them at an optimal temperature during use. Either console may feel hot around the vents, but this is normal. Hot air is being ventilated from the console to cool
the interior. Keeping the console free from obstructions and clutter will allow it to ventilate properly.

For more info:
support.xbox.com/.../ventilation

Having your Xbox One S in a vertical position(without stand) will effectively block the side air vent. This will cause insignificant ventilation, resulting in the console overheating and shutting down and possible damage.

The Xbox One S requires a stand to be used in vertical position, which will allow proper airflow/ventilation.

Ventilation is number one, but it is possible that the xbox one s renders the game this way. It is very graphical intensive.

Ventilation tips for keeping an Xbox One console cool can be found here: Ventilation for the Xbox
One Console

The Xbox One S is mainly ventilated through the circular hole on top, and the sides of the console. I wouldn't recommend keeping it inside a closed space, but if it's getting fresh, cool air from somewhere, and the console is not shutting itself down to
protect from overheating, then it should be okay.

Are you getting any error message? Is your Xbox One S console in a confined space, or is it well ventilated?