Nissan Motor is shaking up its leadership as the Japanese automaker grapples with a growing list of setbacks, from sluggish sales to failed merger talks and looming tariff threats in the United States.

On Tuesday, Nissan announced that Makoto Uchida, its chief executive since 2019, would step down. Ivan Espinosa, a Nissan veteran and the company’s chief planning officer, will take over as chief executive on April 1, the company said.

The move follows a tumultuous year for Nissan, putting the company in a leadership transition midway through a restructuring effort and at a time of heightened uncertainty for the nearly century-old brand.

Nissan said in a statement that “a new generation of leaders” would help position the company for long-term growth. Mr. Espinosa, 46, has held a number of roles related to product planning since he joined Nissan in 2003.

Mr. Uchida, 58, took charge during another turbulent period, after the ouster of Carlos Ghosn, then Nissan’s chairman, on allegations of financial misconduct. Nissan was reeling from a sharp decline in profits, and its leadership was in disarray. Mr. Uchida stepped up after Ghosn’s immediate successor resigned over separate issues involving his pay.

Mr. Uchida, who ran Nissan’s China business before taking the helm of the company, overhauled its decades-old alliance with the French automaker Renault and embarked on a mission to boost profitability by scaling back incentives that had propped up sales during Mr. Ghosn’s tenure.

For a time, his strategy seemed to be working. Nissan reported healthy profits in 2022 and 2023, buoyed by a post-pandemic surge in demand and a favorable exchange rate. But the company’s aging model portfolio struggled to keep up with shifting consumer preferences for hybrid and fully electric vehicles in some of its core markets.

That has been especially true in China, where local E.V.-wielding champions are increasingly outselling smaller foreign brands. Nissan’s unit sales in China fell by more than 9 percent in the nine months through December. Struggling in other regions as well, Nissan cut its profit outlook three times in the current fiscal year.

In November, Mr. Uchida revealed restructuring plans that involved slashing Nissan’s global production capacity and cutting thousands of jobs. At the time, he said he felt responsible for the company’s failure to adapt to a fast-evolving market and volunteered to take a 50 percent pay cut.

Late last year, a potential lifeline emerged for Nissan: the possibility of merging with Honda. The combined entity would have been one of the largest auto groups in the world. But less than two months after the companies began talks, the discussions collapsed because Nissan opposed a proposal from Honda that Nissan become its subsidiary.

Now, Nissan faces a new threat in President Trump’s proposed tariffs on cars imported from Japan, Canada and Mexico. North America is still Nissan’s largest market, and the automaker would be particularly vulnerable to those tariffs. Roughly a third of the nearly one million vehicles it sold in the United States last year were built in Mexico.

Last month, Nissan reported a decline in global sales across its core markets, excluding North America, for the nine months ending in December. Its operating profit also plummeted nearly 90 percent, dropping to $435 million during the April-to-December period. Mr. Uchida warned that tariffs could have a “huge impact” on profits.

The turmoil in the auto industry has begun causing churn beyond Nissan. Other recent high-profile exits include that of Carlos Tavares, who resigned in December as Stellantis’s chief executive amid declining profits and sagging sales in North America.