over-concentrated on breathing

I just had a 1 hour nap.
There was like 15 minutes when I was awake and with my mask on.
During that 15 minutes, I was aware of my breathing and I actually felt tired breathing so there were stoppage of breathing before I was asleep.
I looked at my data summary right now and it said I had a period breathing rate of 9 % and ahi of 13.5 compared with my 5.3 recorded last night.

Do you think it was the machine that mis-interpreted it or did I really have central apnea?
And is it normal that I feel tired breathing when I am awake?

The machine does not interpret 'awake' breathing patterns, at least not the same as it does asleep ones, and it won't give a valid summary even of asleep breathing unless you go 4 hrs on it. Stop thinking about your breathing - have a white noise source on, read yourself to sleep (with the machine/mask on), take 1 mg of Melatonin an hour before bed, etc. etc. It is common and normal, however, to do some periodic breathing as you're falling asleep and just before waking, so don't fuss about it if it shows up on reports now. The feeling tired thing I think could be just anxiety... don't worry about it.