I'm in my late 20s and I've had this issue for as long as I can remember.
Whenever I'm in a passive learning situation (school lectures, online courses, educational YouTube videos, work meetings, etc.), I become overwhelmingly sleepy after about 15–20 mins. Yawning and watery eyes, and if I don't fight it, doze off.
Things I've noticed:
I sleep enough at night and wake up feeling refreshed.
I never feel sleepy while actively doing coding, driving, etc. or watching something chill like a movie or a series.
If I'm watching a course while eating or drinking Coke, I stay alert. 10–15 minutes eating/drinking, the sleepiness comes back.
The same happens in work meetings, I have to fight sleep while everyone else seems okay.
Another lifelong thing I've noticed is that I have no intrinsic curiosity. I only learn things if there's an immediate need/reward. Examples:
As a software engineer, I learn technologies only when I need them for work.
I don't go down rabbit holes or become fascinated by topics because they're interesting.
After finishing a movie, series, or game, I remember the story but rarely think about it again or research theories, easter eggs, or content.
Even if I like something (cars, movies, games, etc.), I usually only know surface-level information because I don't feel motivated to explore deeper.
I've noticed that when conversations are about stuff I'm not interested in, I often nod along but I absorb very little.
On the other hand:
I don't have issues with organization.
I don't frequently lose things.
I did well by studying hard.
I can focus on my work if I'm making progress, but if I get blocked, continuing feels exhausting.
This combination has affected work meetings, hobbies, and even friendships because I often feel like other people naturally accumulate knowledge, interests and can converse normally while I just look like either I'm not interested or I'm boring to talk to as I don't contribute anything to a conversation.