What causes normal breathing to stop or oxygen intake to be insufficiet to support life?

LOL what u ask is like aswered by probably 3/4ths of the causes of death .... be more specific swts

A bullet to the heart usually stops breathing, A volcanic Eruption where Volcanic gases replaces all the Oxygen with Toxic gases

You need to be more specific.

There are a million answers to this question.

There are numerous conditions/diseases that can cause this. It could be a neuromuscular disease that if it affects the muscles of the lungs and diaphragm, you will go into respitory arrest. An allergic reaction to allergens can cause this also.

If this has happened to you, I would consult with a pulmonary specialist to have a lung capacity test.