could be a leaking injector, fuel pump dying, battery, alternator, loose wire on starter or maybe even temp sensor.
Best bet if you can is to swap or unplug stuff till you get a result. Dont go buying anything until you know for sure though, jus borrow off a mate or failing that I'm sure someone on this forum would lend you some parts. I have an old fuel pump and alternator lying around if you need. GL