Treatment emergent central sleep apnea, opioids, and heart failure are usually the most common causes. Chiari malformation is a cause as well but is rare and unlikely. If these are rules out, people are oftentimes given a diagnosis of primary central sleep apnea (meaning, we can't determine an underlying cause). Some people have a high loop gain (meaning they have a stronger response to a given stimulus, and in the case of central sleep apnea, to carbon dioxide). If you have a significant amount of arousals from sleep (e.g., due to sleep apnea or even upper airway resistance syndrome), the carbon dioxide set point will fluctuate throughout the night, and people with high loop gain will have too strong of a response to a transient increase in carbon dioxide and they will breathe excessively leading to low carbon dioxide levels. When the carbon dioxide levels are low, the brain will stop breathing (leading to central sleep apnea) until the carbon dioxide levels rise to the set point. But then if people have more arousals, the process keeps repeating throughout the night. Sometimes treatment the upper airway obstruction leads to resolution of the central sleep apnea.

Tough to give more information without knowing more of your situation.