There is a check valve in the fuel pump, replaceable, that can lose pressure, bleed off fuel from the line. When it's cold the cold start relay blasts the fuel into the system to get it going. Warm engine, should be fuel present, or so it thinks. It is a royal pain, but I had to rely on a can of starting fluid to get me going with a warm engine until I replaced that little valve on the pump. May or may not be your problem, too.