Son that sleeps a lot

Our son is 23 and living at home with us for a few months while he buys his first home.
He has always been very successful in school, his career, and anything he takes part in he is always spotted as a leader.
He was student body president, 4.0 student in high school and college.
Very well liked and respected.
He works full time, goes to the gym after work, volunteers, active in church, girlfriend, lots of friends.
He is very much an introvert.

He has always been a sleeper. He slept through the night from 8 weeks on.
He really feels best when he gets 9 to 10 hours sleep, this is nothing new. He is healthy, just had blood work done.

When he would come home from high school he couldn’t get through the door quick enough and wanted to take a nap.
Now on nights when he doesn’t have anything he has to do after work or on the weekend he naps for 2 to 5 hours.

He has said he enjoys sleeping alot.
I have talked to him about this before and he says he just puts out so much into the world that when he gets home he just wants to be quiet and sleep.

So all this to say. I know its his life and he is very successful.

But my question is as a parent, how do we know this isn’t depression.
I think there are 3 possibilities,
Depression, or he can’t manage his emotions so he goes unconscious when he gets home-buffering, or he really just likes to sleep.

The only reason my husband and I would have a serious talk with him is because I don’t want to be parents that were afraid to bring up his mental health and then something happens. I think he carries around a lot of frustration.

Any way how can we can bring this up without saying we are worried or are you depressed and infringing on him as an adult?
Or are there questions I could ask him to find out if he is just buffering to check out?
We want him to know he can get help if he does in fact feel depressed or unable to cope in the world.

Thank you!