on your vehicle the fuel pump does not start to work till the engine turns, it get it signal from the distributor, what happens as it gets older the fuel pump and regulator ( which is in the tank ) tend to get weak and will need replacing soon. what you can do is cycle the key twice making sure you click the engine and on the third time it will start with no problem
the reason why it's happening is the fuel is leaking back down past the regulator and punp assembly when vehicle sits for a bit
