Electrical problems with my Kawasaki ZZRj 600?

Okay. So I was at an atm, and left the key on for maybe 3 minutes. Not even.. Keep in mind, I've never had a problem like this before..
Anyway, I flip the starter on and it cranks, but the lights started dimming and after a 3rd try, it just dies. So I ended up waiting about 20 minutes before trying again, and when I do it starts. I don't understand what happened. Cause it wasn't starting at all, and then it did.
Is it the battery? Connections?

FYI, I have no idea on what to do. Absolutely zero skill set in this. So if you through any mechanical tips, I might need a walk through. I don't have an owners manual and I really need one, and the bike isn't very popular at all so finding others with the same bike wouldn't be easy....

ANY HELP PLEASE.