crazy instrument panal

I have a 2004 nissan titan and today i unhooked the posititive terminal on the battery cleaned the battery terminal and the connector rehooked it up and started the truck and all is fine for about 3 seconds and then the instrument panel starts going crazy like the temp gauges go from normal to zero the slip light comes on the rpms go normal idle to zero and back up to normal along with a few other lights any ideas why