The FI relay on the left inner fender well just behind the battery would also be my first guess. It's one of the smaller ones in that location, but it doesn't really matter: it's probably a good idea to clean all electrical connections in that area. The large relay is for hi/lo beam switching, I think the only other thing there is a positive connector, covered by a plastic housing.
Take the connector off the relay, clean the connections with sandpaper and then an electrical contact cleaner (esp inside the connector, where you can't reach with sandpaper.
The big plastic relay by the hood release is the fuel pump relay. It shuts off the fuel pumps if it doesn't get a signal from the ignition coil (as if the engine stalls in an accident).
I have heard of the ignition switch causing some of the electrical accessories to work intermittently, but not the engine itself, altho it is possible I guess. But in that case wiggling the key should have some effect...
HTH,

Balu