No power at all
 

I am new here but have been doing work on my jetta since the warrenty ran out. In the last two weeks my wife and I have gone out to the car (2002 jetta 1.8t) and found that it has no power at all. The alarm and everything is off, so I use the key to unlock the door and pop the hood, look around a bit and see nothing. I get in the car and shut the door and everything comes on like there was no problem. So we come to find that when the power is off like this, has happened maybe 8 times in two weeks, we can slam the door once or twice and it comes back on. I figure it is a ground or loose wire, so I went through what I can get my hands on and everything is connected and tight, no corrosion problems. Is there something I am missing or maybe another connection I can take a look at? Oh, I also made sure all of the fuses, engine and interior were good and there was no problem there either.
Regards
Cbass