Final answer:
Nichole most likely has sleep apnea, a disorder characterized by pauses in breathing during sleep due to physical blockage of airflow, leading to disruptions in sleep and various symptoms.
Step-by-step explanation:
Nichole most likely has sleep apnea, which is a disorder characterized by pauses in breathing during sleep. These pauses are usually caused by physical blockage of airflow. When breathing is paused, carbon dioxide builds up in the bloodstream, causing the respiratory centers in the brain to wake the person up enough to start breathing normally again. This disruption in sleep can lead to fatigue, irritability, memory problems, and other symptoms.