(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window.) * Energy sector down after hitting highest since Jan 2020 * Big banks set to start reporting results from Wednesday (New throughout, updates prices, market activity and comments to close) NEW YORK, Oct 11 (Reuters) - U.S. stocks ended a choppy session lower on Monday as investors grew more nervous ahead of the third-quarter earnings reporting season. Supply chain problems and higher costs for energy and other things have fueled concern about earnings, set to kick off with JPMorgan Chase & Co results on Wednesday. Indexes reversed early gains, and JPMorgan shares were down and among the biggest drags on the S&P 500, while the S&P financial index was also lower. According to preliminary data, the S&P 500 lost 30.56 points, or 0.70%, to end at 4,360.78 points, while the Nasdaq Composite lost 95.94 points, or 0.66%, to 14,483.60. The Dow Jones Industrial Average fell 252.12 points, or 0.73%, to 34,494.13. “I was surprised to see the market up this morning because earnings season is right ahead of us, and the market is a bit cautious going into this earnings season,” said Tim Ghriskey, chief investment strategist at Inverness Counsel in New York. “Supply chain issues may have impacted earnings for a number of companies and certain industries more than others.” Another period of strong U.S. profit growth is forecast as third-quarter reports from Corporate America flow in starting next week, with analysts expecting a 29.6% year-over-year increase in profit for S&P 500 companies in the third quarter, according to IBES data from Refinitiv as of Friday. But earnings are shaping up to be crucial for investors worried about the impact of supply disruptions and inflation pressures on U.S. companies, and could lead to more volatility on Wall Street following a bruising September. Energy was also lower after hitting its highest since January 2020. Higher oil prices have fed into concerns about rising costs for businesses and consumers. Some trading may have been affected by the U.S. Columbus Day holiday, with U.S. bond markets shut on Monday. Among individual stocks, Southwest Airlines Co slipped on a report that it canceled at least 30% of its scheduled flights on Sunday. Additional reporting by Shreyashi Sanyal and Devik Jain in Bengaluru; Editing by Arun Koyyur, Aditya Soni and David Gregorio Our Standards: The Thomson Reuters Trust Principles.