02 Jeep Grand Cherokee wiring issues?

I recently bought an 02 jeep grand cherokee with a 4.0 straight 6. I haven't had it a month yet and things are starting to worry me. First the blinkers quit working. I shut it off and started it again and they started working again. The flashers worked when the blinkers wouldn't. Then today, I got in at night and my instrument lights and all of my dash lights were very dim. If I didn't have good eyes, I wouldn't have been able to see it. My mom had a similar problem with her 02 cherokee and it was a wiring problem with a lose wire losing connection in the door? I remembered her saying that, so I slammed my door as hard as I could and everything started working again as if nothing was wrong. When it wouldn't work, I would get a message where my outside temperature reads (not sure what that is called) and it said my driver door wasn't closed. I don't believe it was the door jam switch causing it, as it wouldn't have made the dash lights dim, and the interior lights wouldn't have went off. Does anyone have any idea on what this might be and where I need to be looking? I'm fairly car smart but no mechanic by all means lol