Electric issues with Mercedes S500 1995, cluster fluctuates

What is your question?

I am perplexed on what's the problem after changing most parts and the wiring harness, etc,.. I started it and it was fine, the next time I tried a start upon turning the key into 2nd position, the cluster started blinking and the needles were going up and down. After I take the key out, the needles vibrate slightly. Upon disconnecting the battery, every thing goes back to normal. As soon as I reconnect the battery, the needles vibrate again. Also replaced, distributor caps, rotors, fuel pump, crank position sensor, new spark plugs and spark plug wires and ignition coils. Please help Johnny5 needs input. Thanks in advance.

What makes this problem better or worse?

Electrical

How long has your 1992 Mercedes-Benz 500SL had this problem?

Since purchasing car