Andrew Barth Feldman, left, and Jennifer Lawrence in “No Hard Feelings.” Macall Polay/Sony Pictures Entertainment

In the blandly inoffensive sex comedy “No Hard Feelings,” Jennifer Lawrence plays Maddie, an emotionally stunted, sexually liberated 30-year-old living in her childhood home in Montauk, studiously avoiding the bonds of adulthood. As the movie opens, Maddie’s car is being towed for back taxes, a catastrophe of financially epic proportions, since she’s an Uber driver.

And then, voilá: Maddie spies an ad placed by the prosperous helicopter parents of a 19-year-old who is starting college in the fall; in exchange for “dating” their son, they promise a willing young woman a Buick LeSabre, free and clear.

It’s an outlandish premise, meaning there’s no surprise in learning it’s reportedly based on a real-life Craigslist ad. Such are the times we’re living in that hypervigilant parenting, transactional sex and the gig economy can take up inordinate space on a Venn diagram. The contours of “No Hard Feelings” are also immediately familiar: Percy (Andrew Barth Feldman), the teenager in question, will be matriculating at Princeton, which can’t help but evoke Tom Cruise’s similarly Ivy-bound Joel Goodson in 1983’s “Risky Business.” The film’s lineage goes back even farther, to “The Graduate,” of course, as well as the Doris Day de-virginization farces of the 1950s and 1960s. A common reason proffered for the lack of big-screen romantic comedies is the challenge of credibly keeping a modern-day couple apart; “No Hard Feelings” solves the problem by making Percy the last 19-year-old boy on planet Earth who’s reluctant to lose his virginity, even with Jennifer Lawrence at her most lasciviously unhinged.

The twist is that Feldman makes it work. “No Hard Feelings” isn’t a great movie, not even a very good one – but it ambles along with frictionless ease, mostly thanks to the low-key naturalism of its stars. Directed by Gene Stupnitsky from a script he co-wrote with John Phillips, “No Hard Feelings” consistently pulls back from its ickiest plot points to reveal the wholesome heart at its center. Maddie isn’t a predator or a mercenary; she’s a wounded and abandoned child. Percy isn’t a gawky loser; he’s an unusually gifted kid with a stronger emotional core than most grown-ups.

In other words, there will be more hugging and learning in “No Hard Feelings” than anything shocking or explicit – which isn’t to say the movie is entirely chaste. Lawrence bares all for a bizarre fight scene she executes entirely in the nude; Feldman gets naked for his own set piece, atop the hood of a speeding car. Racy double entendres abound, with groaning results. By turns giddily coy and disarmingly frank, the movie doesn’t know if it wants to be a kinder, gentler Apatow or go full Farrelly.

Amid all the unevenness and tonal inconsistencies, though, something genuine emerges: Lawrence isn’t as gifted a comedian as, say, “Trainwreck’s” Amy Schumer, but she exudes authenticity and warmth that are hard to resist. Even more appealing is Feldman, who delivers an adroit breakout performance as a young man who’s both ridiculous and heartbreakingly vulnerable. He nails Percy’s comic beats with sublime timing and expressive control, then spins on a dime to deliver a meltingly plaintive rendition of Hall & Oates’s “Maneater”; the result is a character who feels fully inhabited, despite the generic constraints that bind him.

Despite its shaky fundamentals, “No Hard Feelings” feels of a piece with Stupnitsky’s most recent hit: the viral sensation “Jury Duty,” about a naif surrounded by people who are more in-the-know than he is. What seems to start out as an exercise in cynicism turns out to be a bracing testament to human kindness. “No Hard Feelings” may not stick the landing with quite as much ingenuity or energetic wit, but it’s powered by the same brand of humanism. It earns its title with a harmless, good-natured shrug.