Normal. It is called " Dieseling". The simple design of the engine is like the old ones unlike today's diesels. It is from incomplete combustion of a cold engine, as the engine starts to warm up, it will burn the fuel more efficiently.
2021 Ram Limited, 3500, Crew Cab, 1075FTPD of Torque!, Max Tow, Long bed, 4 x 4, Dually,
2006 40' Landmark Mt. Rushmore