I'm late to this one, but the most common symptom is extreme sleepiness during the afternoons, even to the point of narcolepsy. It'll cause all kinds of havoc with your sleep routines.

I got suspicious after falling asleep at work a few times, just an unbearable sleepiness, like I had just taken Benadryl and some vodka. Turns out I had sleep apnea to the tune of 61 events/HOUR.