I have a 98 f150 4.2 5speed, every now and then it will just shut off randomly and if I instantly try to start it up and just cranks and cranks and nothing. If I wait 30-60 seconds it fires right up like nothing happened. Was told maybe back pressure issue considering it could use exhaust work. Cats are hollowed out and no muffler. Not sure if that's the cause or maybe a fuel issue?

 

Check the OBD codes and see if any are set. That would tell you if you had a bad cam or crank sensor, or another issue.