2000 Grand AM Acting Strange

[lisamd]

I own a 2000 Grand AM and it has been acting strange for sometime. I have taken it to mechanics and they can;t find out what is wrong with it. There are many things it does like: when i brake the radio will flicker off then back on, or sometimes it turns right off, my llights will dim when i brake, when i blinker my lights flash with the blinker, when i brake some of my dash lights come on like my ABS, and parking brake light. The other day when i was driving, my car just shut right off (it has done this twice) i thought maybe it did this because i was trying to use extra power (i turned on my ac). Then sometimes after i shut off my car, it will not start back up, when i try to start it i don;t get any power. If i unhook the battery and hook it back up it will start back up and then it runs fine. I have had a new battery put in and my alternator checked.
Please Help!!

[GTP Dad]

Check the car for loose or bad grounds. Due to the fact that problems are intermittant the issue has to be electrical in nature. Once you check all the gounds then check the hot wire leading to the power control center under the hood. Most if not everything is controlled from there and if you have a bad connection the car will do just exactly what you are saying. Also check the wire connections at the starter.