Tiredness of sleep apnea can fluctuate during the day?

Yes, certainly, but it could be other things that also should be ruled out. Brain chemistry, endocrine system health, essential nutrients and electrolytes, a disease hitherto undetected, pulmonary health. I only add this for an attempt at completeness, not to suggest that you are necessarily barking up the wrong tree with respect to apnea; get the apnea checked out! Sleep apnea, if bad enough, has its hosts falling asleep at longer traffic lights!

@robertwills
I have sleep apnea and 55, female. Your description sounds like my symptoms before diagnosis. It would be good to get a sleep study done and check blood for deficiencies/toxicities. I drink too much caffeine which doesn’t really help sleepiness and causes other symptoms and problems. If you are managing caffeine and screen time before bedtime and not having anything in your diet or supplements causing sleep issues, it may be sleep apnea which is really important to diagnose/treat.

It seems like you have a lot of questions and concerns about sleep apnea - do you think that you have sleep apnea? As everyone says in their responses, you should probably get checked out for sleep apnea.

Unless your partner hears you stop breathing for 34 seconds and then take a deep breath, I don't think you can try to diagnose sleep apnea from how you feel.
At the least do a home study, can find some that are not too expensive.
You will be surprised .

I was very sleepy and had my blood tests done and it shows very low levels of cortisol and I e been referred to endocrinologist so you never know to be honest. Best way is to get checked for everything really, good luck! 🤞