Hi all!

I have a 2001 GTP that has been giving me some problems.
Sometimes when I touch some of the wires under the dash/ in the doors, or when I hit buttons on the dash (rear defrosters), and my car is off, the car will not start... I will put the key in the ignition and and turn it and then nothing, doesn't turn over or anything. When this happens, sometimes some of the lights and electrical parts will still work, sometimes they wont. To get the car back stated I hook the battery up to my 50amp battery charger, and within a couple of minutes it starts up like nothing happened.

Ive had the battery and alt tested, they are good.

The first time it did it to me I was sitting in the car, with it off, listening to the radio. I hit the rear defrosters and the dash lights dimmed. I then tried to start the car and it wouldn't turn. From there it happened once when I was working on a speaker in the door, and when I was pulling working on the steering wheel.
The guy i bought the car off of had subs and an after market alarm in the car, he took out the subs before I bought it and I took out the aftermarket alarm because I thought that might be what was giving me the problem (it didn't start again after I pulled out the alarm).

Its doesn't make any sense to me and I was just wondering if any of you guys have heard of anything like that or might have any tips. my best guess so far is a loose ground.

PLEASE HELP!!!