I don't know much about your physical state. So, let me just put out some generic advice.

1. Enough quality sleep. 2. Exercises that involves your legs. Somehow leg muscles help the heart to pump the blood back up, keep enough pressure and circulation in your brain.

I'm 35 and I've already experienced the benefit of those 2 and the negative impact of lack of those 2.

Maybe you could be just rusty about that kind of code?

Was going to post this. I become a foggy-headed moron when I don't do these things, and I'm plenty sharp when I do.

My area is blessed with parks and cool places to go for a walk, I hope you and OP have something similar.

I would add that, if both sleep and exercise don’t seem to solve it, then sleep quality (e.g., sleep apnea) could be an issue, especially if a person is overweight or has other health issues (e.g., bad allergies).