Is it normal to think.. too much stuff?

I think a lot, a bit too much. I just didn't know what to put as the title but I have this one thing, that sometimes, out of nowhere situations and like other people's conversations pop in my head. It isn't like hearing voices but kinda since I have no control of them (what they say or what image do they paint in my head) and after that they just dissappear
That happens a lot when I space out and always when I space out, I really can't snap out of it until I start panicking that I can't go back into reality.
Are these things normal? And if not, what the fuck is wrong with me?