Question from a 30s something-er

I thought this was a pretty good place to ask this.

So I'm in my late 30s, and it's been several months now that I:

- keep feeling tired, it's hard to make a physical effort, even though I always used to

- my legendary memory has been downgraded to just decent

- started wearing glasses to watch tv

- focus isn't what it used to be

This may sound silly, but apparently, until now, I lived thinking that the condition of the body does not undergo any degradation until one is quite close to the end of their life(yes, I realize how naive this seems. I don't really know what to say).

My question to you, dear 50somethingers, is this: do you think that this is normal to experience in my late 30s, or is there some health issue I should look into? Thank you for reading.