Hi Raquel2.
My symptomes are very similar to yours. I am 64, male, and have been diagnosed with sleep apnea about a year ago. To majority of apnea events are central in nature. Doktors have no explanation. I do not fit in the typical sleep apnea patient pattern. With CPAP I can manage to keep my AHI around 10.
My worst events are those you describe. As I relax and transist into sleep I wake up and notice that I have stopped breathing (Scary!). Sometimes my heart rate goes up to 120 or more. One or two such events occur in the first hour after going to bed. Then for the rest of the night no such events occur anymore.
I have started to notice some triggers. If I avoid them, things are much better. Typically, if I spend several hours watching TV, working on the computer or looking at my mobile phone screen, these events occur frequently. When I avoid those triggers after 6pm these events are less frequent.
Another trigger I noticed are many hours driving my car.
I typically get up around 4 or 5 am for a visit to the bathroom. I noticed from my CPAP recording device that when I go back to bed after those bathroom visits, my AHI score shoots up quite a lot. So in general the average AHI of around 10 over the whole night is mainly due to the last third of the night.
I think in my case it is self-induced mental stress that is a factor. So I am starting to explore medition, breathing stress management exercises.
There may also be a serotonin link. I had a genetic test taken (cost me 200 Euro). Apparently, I am very low on serotonin. So I hope by improving my diet and using above techniques, as well as taking L-Tryptophan supplements I can make improvements.
Also, and I have reported this in this forum, when I have a decent amount of alcohol (in the order of 5 pints of beer or a bottle of red wine), my overall AHI through the night drops to 4-6. Still, the last third of the night is manly responsible for this total average.
I have no blood flow issue in the brain.
Best regards
Deepnap