If it is the Neg Cable you are wiggling and it will start then yes most likely is is either a grounding problem or a bad cable.
What you can do is remove the Neg Cable completely from the car. Check it for cracks in the casing and corrosion. If it badly corroded replace it. If looks in good condition put it back on making sure the connections are clean, especially on the engine side, and tight.
Saturday, May 30th, 2009 AT 8:46 AM