W202 headlight bulb doesn't always light
 

My wifes 98 C230 had a headlight buld out last week. I wiggled the connector at the back of the buld and the headlight worked. Sje told me a week later it was out again. I just wiggled it again and it came on. Any idea what is causing this. Corrosion??

Could be corrosion on the connector. Sounds like it might possibly be a wire with a break. While it is in a stationary position it has continuity and current passes thru to the bulb. If it moves a little, the wire strands separate and current stops passing through to the bulb.