It sometimes feels like that is by design! Can't have people knowing they can experience a break from all of the chatter, can we? ;-)

Many types of meditation is designed to get this result, but some people experience these states spontaneously. Some know them and can go in & out of them at will, I knew a German who claimed he could do that, he mentioned it as a simple matter of fact without any pride in it, so I believe him.

Yes, and no. It depends what you understand by "meditation"

I think anyone can achieve it, and does it to a certain extent more or less regularly, when the conditions are right, i.e. when not distracted. Professional athletes, and creative people like artists, when performing, are so focused that they get there instantly. They call it "flow"

In my personal case, my most vivid experiences were while spending a week on my own in a remote forest cabin, silent. The other time was while swimming a long distance in the sea...