I felt that there was something wrong with my sleep, so I bought a Samsung Galaxy Watch 8 to monitor myself. I asked it to check for Obstructive Sleep Apnoea, which it did over the previous two nights (28th Feb and 1st March) and came back this morning saying that indeed I did have apnoea:

I had a look at the graphs of blood oxygen (SpO2) for the two nights:

The watch checks for snoring as well, and I snored for about half the night.

I made an appointment to see the doctor and she rang back this morning and asked me to fill in a questionnaire to determine my score on the Epworth Sleepiness Scale. I never actually fall asleep during the day, so scored in the normal range. But thankfully I was referred to a sleep specialist anyway, presumably because of the measurements, snoring and my feeling of poor sleep.

I know that being overweight is a risk factor for OSA, and I am overweight, so I've gone on a fasting diet. The fast is daily, from 20:00 in the evening to 12:00 the following day. I've fairly recently given up drinking alcohol, so that should help too.

I possess a CPAP machine, and I tried this a few days ago for one night, but I didn't feel any better. My plan (starting this evening) is to get my watch to do another sleep apnoea test, but this time with the CPAP machine.