This one might confuse people but it happens. Sometimes people stop breathing for a few moments without realizing it. This is known as apnea which usually happens when they’re asleep. It can last between 10 and 30 seconds before the brain comprehends what’s happening.
It won’t shock anybody to learn that this isn’t healthy and can even be life-threatening. Often victims won’t realize that they have a problem unless it happens when they’re awake. Sleep apnea can be a symptom of a brain tumor because the neural passages aren’t sending messages to the lungs. (via Cancer.net)