bathroom light flickering?

i have a two-bulb bathroom light fixture. the left bulb randomly flickers, sometimes shuts off completely for a couple seconds. i figured it was a loose wire inside the light, but shaking or bumping the light has no effect. it can't be a fault from the switch to the wall, or else both bulbs would be flickering. any takers?

Public Comments

1. I'm guessing there is a loose wire in the circuit (after the switch; probably in the fixture) that goes to the left bulb, or there are loose mechanical components or connection(s) in/at the left socket .
2. The two lights are wired in parallel. If the first light is steady and never flickers, then the problem is probably the parallel wires between the first light and the 2nd light has a loose connection between the two. And of course, assuming the bulb is not loose in the socket (should be snug, but not too tight)