One thing you could ask about would be:
Sleep Transition Apnea
Sleep transition apneas refer to the fluctuations in ventilation that occur in otherwise normal individuals during the transition from wake to sleep.
“**Regardless of the underlying cause of arousal from sleep** (ie, spontaneous arousal, periodic leg movements, respiratory load induced arousal), **an individual with a low arousal threshold** (ie, susceptible to waking up easily) **will be vulnerable to sleep state instability**. That is, the combination of a predisposition to sleep transition apnea and a low arousal threshold may be sufficient to facilitate a repetitive CSA cycle as the individual oscillates between wake-fulness and sleep. The arousal threshold does, however, increase with progressively deeper sleep stage, as does breathing stability provided slow wave sleep can be achieved. However, it remains controversial whether slow wave sleep is intrinsically more stable from a respiratory standpoint, or if stable breathing allows sleep to deepen.”
From what I understand this can also happen during the transition between sleep stages.