Cars dies no power
 

Hi i bought a 1998 Mitsubishi Eclipse spyder, but im having problems keeping it on it keeps dying. Like 0 power on the whole car. Battery is good and so is the alternator. Today i started the car twice amd it started , but when i wanted to start it for a third time , dead no power no lights no nothing.!
I could only restarted with a booster. Yall have any ideas?