car dies then comes alive later

[HiImBrian]

Well I just got back from Ames a few hours ago and I was pretty happy considering zero car problems on the way home is exactly what I like to see. Well after I got home, I relaxed for 15 mins before I went back out to unpack the car. I got outside and opened the passenger door and the dome light didn't turn on, but I didn't really think anything of it. It ended up coming on about a minute later by itself anyways. Well after I unpacked the car I locked it (using the aftermarket keyless entry system) and went inside. Later when I went outside to move the car so my dad could get out the car was completely dead. Now I know nothing was left on or open. It just had no power. It was about midnight and I wasn't about ready to use the key to unlock the door and risk setting off the alarm so I decided to just leave it. Later I realized the alarm wouldn't even go off if the little flashing light was off. So I decided to go back outside and check. I hit the unlock button on the pad and the car chirped at me and unlocked. I got in and it started up just fine like nothing happened. What the heck is going on here?