Summers here and I'm having a hard time getting My 1988 300TE to start when hot.

OK, in Feb I had a valve job done and head gasket replaced and a few other parts. The shop told me that my fuel pressure regulator was not so good so I replaced it. The problem is the car starts ok in the mornings and it will start right up after you shut it off. But if is sets for 5 min or more it has a hard time starting backup. and when it starts it acts like it is out of gas and has a ruff idle but then smooths out after 30 sec or so. The problem get worst as it gets hotter out.