Why won’t my car start?

I have a 2004 Jeep Liberty and I got the car on Sunday on Monday I didn’t start it but on Tuesday I did now today is Wednesday and when I went to start the car there was a noise in the hood so I left it on start but with the engine not on when I noticed the lights on my dash were blinking then the car turned itself off completely I decided to give it some time to rest while I sat in the car with the keys in my hand I heard a noise from the trunk which seemed to be the trunk attempting to open but it wouldn’t my battery is only one year old I really don’t want to put more money into this car than I have