Why would someone someone hyperventilate excessively then go completely apneic?

Alkalosis: Rapid breathing makes your blood alkaline. Absence of breathing makes your blood acidic. Your breathing is also regulated by your oxygen level in your blood/brain. Desire to breath, though is driven by your acid/base balance in your blood. As a result, your body going apneic is its response to re-balance it's blood ph to normalcy.

R/O OSA: OSA can be suggested by history and physical. Excess snoring/daytime sleepiness/apneic episodes/ aM headaches. And the Exam obesity/small oral airway/collar size>18. The definitive test is a PSG with split night/CPAP titration. I would request copy of sleep study and get a second opinion if you are not satisfied with the options. You are young CPAP can be difficult to tolerate. ENT FOR UPP EVAL.