The singer, 46, will rock New York City's Hammerstein Ballroom
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Gwen Stefani is casually talking about the joys of performing when she bursts into song.

“I love going, ‘Uh huh, this my s—,'” Stefani tells PEOPLE, recreating the refrain in her 2004 hit, "Hollaback Girl."

The singer, 46, spent her Friday afternoon at New York City’s Hammerstein Ballroom, where she will grace the stage on Saturday in her first solo concert since February.

“I love you, New York!” she says with her trademark gusto.

But then, reality sets in: “I’m not ready yet,” she says. “I still have a rehearsal today. I get to do one more rehearsal. I think, after that, I will be.”

The No Doubt frontwoman isn’t on a giant arena tour she’s been planning and rehearsing for months. Instead, she’s taking the stage as part of MasterCard’s Priceless Surprises series, which is all about creating unique special events for fans.

“It’s a surprise they wanted to work with me, first of all,” she quipped. “Part of the whole thing was, ‘You gotta do these shows.’ I was like, ‘Well, I’m not really doing those songs anymore, but okay.”

Stefani soon found herself struggling to put together a show in Los Angeles featuring her hits from the 2000s.

“It was so hard because I had nothing,” she explains. “I had not done the songs in eight years, I think. I had no band, no dancers, no costumes. I had to do everything in two weeks, which is impossible.”

Just because the blonde bombshell has been wowing mainstream audiences since No Doubt’s “Just a Girl” became a hit in 1995 doesn’t mean she’s immune to nerves.

“The day before, we were in my kitchen, and I was like, ‘This is the one time it’s not gonna come together; it’s over for me,’ ” she says.

Stefani lets out a good laugh before sharing the silver lining: “And then seriously, it was just like magic. The [concert] was incredible.”

She added, “I get to do it again, but in New York, the coolest place in the world.”

Stefani has been busy working on her third solo record, performing shows with No Doubt and judging this season of The Voice. And she’s done all of it while raising her three boys – Kingston, 9, Zuma, 7, and Apollo, 19 months – with ex Gavin Rossdale.

“I [haven’t played live] a lot in the past few years – I had the babies,” she explained. “But once I get up there again, I realize I like doing it. A lot.”