Start with a battery check, Put a volt meter on the Battery and crank the engine, if it goes down below 9.5 volts it is dumping the memory. A bad battery is hard on the starter too. Or cheat and take it to a auto parts store, with hopes that the guy using the tester know how to use the equipment.
If that checks out, head to the wiring diagram and trace the wiring looking for a bad connection, I recommend starting at the component that is failing while checking for a voltage drop while in operation. What I do is put the positive lead on the positive battery connection and use the negative as a probe. If you get a low reading that will tell you the circuit is ok. If you get a high reading that will tell you you have a bad connection.