Weird electrical issue need help

I have a 1996 Pontiac Sunfire 2.2

When starting the car all lights on the dashboard come on. Now they should go off as sensors read outputs. This does happen sometimes. I recently put a brand new battery, alternator, plug wires, battery cables. The odd part is that sometimes the lights go on and off randomly even while sitting idleing and not even moving. Turning the steering wheel causes the lights to go on and off, changing gears (automatic) does the same thing. While driving the lights will come on and somtimes stay on even the daytime running light indicator will begin to flash? The tach will drop to 0 and then jump back up even though the car does not stall. The most aggitating part is if the car does not start the first time the Theft system kicks in and cuts off the fuel sorce not allowing the car to start for 15 minutes.

Please help I am lost is it a computer issue? Bad ground? I dont know what else to do and the mechanic I use dont mess with to much electrical problems.