The phrase "a sort of pop up" is correct and usable in written English.
It can be used to describe something that appears suddenly or unexpectedly, often in a casual or informal context.
Example: "The website had a sort of pop up that offered a discount for first-time visitors."
Alternatives: "a kind of pop up" or "a type of pop up".
So I like this new work by the Itinerant Museum of Art (ItiMa), a sort of pop-up show, which is called Gender Equality?
Guided by Mr. Maccioni, the Holland America Line now offers passengers "A Night at Le Cirque," in a sort of pop-up site with the same menu, décor and orange plates that the restaurant is known for.
He listened attentively to the story, which was a sort of pop-up book, and his little hand emerged between the bars to help pull the tabs that set off the special effects.
"All of the Irish sort of pop up to the surface in New York in March," Mr. Phelan said, his soft brogue still evident even after living in Freeport since 1970.
They are probably more familiar with the random videos from friends that sort of pop up in their News feeds.
"They're sort of popping up all around the L.A. area," said Aurisha Smolarski, a spokeswoman for the Los Angeles County Bicycle Coalition.
She had made a deal to do a show at Fox, and we were sort of talking about the kind of show she ought to do and the kind of people she ought to play and what people expected of her, and then lo and behold the show just sort of popped up and started barking at me.
That happens to be the domain I work in, so that's where I think the future is and my experience in the past is the future sort of pops up from left field somewhere and the next thing I know, there's this very interesting study that has nothing to do with anything I do.
So, these songs just sort of popped up, and the initial kernels came out of the air between the things that we are dedicated to.
Batman's sidekick sort of popped up at the end of "The Dark Knight Rises," but we're, at least, pining for more Robin in the forthcoming "Man of Steel" sequel.
I did, however, naively include a few thumbnail images of cute sex toys, along with a bunch of active, live links to NSFW content, assuming that, being mere links, and being in the MOAN section (which was surrounded by all sorts of pop-up warnings and caveats) there was no way anyone could possibly be offended.
