I just got a 2008 Silverado, when driving the it acts like it loses all power ( lights flashing, clicking noises, dash lights ) all flicker off and on and than every thing is fine. When I turn the truck off if sometimes there is no power like the battery is dead. I have a connection on my pos cable about a foot from the battery with 4 wires plugs in, I wiggle that and it starts and runs fine. Dose any one know what that plug dose to and is it common

 

no idea. Post a photo please.
Is the battery cable clamp tight?