I am trying to diagnois an electrical problem

I have 2003 impala, the dash lights and gauges started fiickering and jumping when the key was in the run position. It would start but the lights and gauges were annoying when driving at night, then the radio ans headlights started shutting off on their own. Then it decided to only crank over and start when it was wet outside. Now no crank or anything on the instrument panel except a check engine light. I took the bcm out and re plugged it in, also took battery terminal off and put back on. The car started and acted great, thought it might be the bcm connection. Shut the car off and tried to restart in 15 minutes, no instrument panel lights and no crank. Took battery terminal off for 5 seconds put back on and car acted great until I shut it off and tried to restart 10 minutes later. To restart the car after setting for 10 minutes you must remove battery terminal and replace to start. Once it is started it will run fine, any solutions you can think of?