Something has shifted in the stock market after Friday’s selloff. Longview Economics says it's time to be careful. - Getty Images/iStockphoto Investors who would like to fully focus on the start of earnings season are dealing with a reboot of trade tensions. A fresh China-U.S. spat over shipping is set to take a bite out of stocks at the open. Trade impacts were all but forgotten, Nohshad Shah, head of fixed income at Citadel told clients. “Downside risks remain present (and underpriced). Friday’s news i ...