Como dizer "Surgir do nada" em inglês

My suggestion:

Out of (from) nowhere.

Bye!

I don't know where he came from. I think he came out of nothing.

My general tendency is to use

to come from nothing = for a person to have acquired status, wealth or prominence despite humble origins
to come out of nowhere = for something or someone to physically appear from obscurity

Sugestão:

Appear from nowhere

Show up out of the blue

Example:
2. (adverb) unexpectedly, out of the blue
In a way that was not expected
"her brother showed up at the wedding out of the blue"

Ref. definitions

Mais uma:

I have no idea where he came from. I guess he just popped up out of nowhere.

Out of thin air

Out of thin air: the mystery of the man who fell from the sky. Ref. theguardian

If you travel by car in Illinois you will hear accounts of deer that "popped up" (appeared abruptly/suddently, without warning) in front of the car...

It's a case of "surgir do nada", however such expression is contradictory, a deer had to be somewhere to cross the road...

Oh dear, it's a deer!

Paraphrasing the poet:
Oh dear! Oh dear!
Oh dear deer!
You deer,
You there,
You are such
A small deer, ...