As Wall Street heads into a new quarter, a flurry of President Donald Trump’s tariffs are set to go into effect. That has traders on edge and has helped put US stocks in their worst first-quarter slump in years.Wall Street has been rocked with volatility this year as Trump’s tariff proposals have kept investors in a cloud of uncertainty. The benchmark S&P 500 index is down 4.9% for the year, its worst start since 2022.US stocks were mixed Monday as traders tried to stage an afternoon rally. The Dow was up by around 430 points, or 1%, reversing course after...