Out of nowhere

"He came out of nowhere!" He came from some unknown, or unperceived direction. The exclamation made is often heard when someone gets in an auto accident and has no idea of how it happened.
It can be used when someone 'catches your eye', gets your attention that is attractive to you.

Dal nulla.

That boy who crossed the street when the car was coming, came out of nowhere = Quel bambino che ha attraversato la strada mentre arrivava la macchina, è spuntato fuori dal nulla.

Biežāk to var dzirdēt situācijās, kad kādam nav ne mazākās nojausmas kā šāda situācija gadījās.

Появиться неожиданно, неизвестно откуда вдруг появиться.
"Взялся из ниоткуда".
"Как из воздуха появился".
"Откуда он только взялся!"
"Неизвестно откуда"