2006 Sonata Intermittent Electrical Problems

I bought a used 2006 Sonata last May that is giving me fits with an intermittent electrical problem.  These problems manefest themselves usually when the gas is not being applied, but not necessarily when the brakes are being applied.  The headlights will go off and then come back on; the radio sometimes will go off and then come back on; the A/C fan sometimes sounds as if it has turned off and then comes back on; several times I noticed the ESC light and ABS light come on when the radio and lights and AC turned off and then came back on.  All these happenings have been reported to the Hyundai service department but they say they can't get it to repeat the symptoms or find a problem.  I can believe they can't find the problem, but I can't believe they haven't experienced what I do every day.  Has anyone out there experienced similar things with their Sonatas?  According to the factory they have never heard of anything like this before and don't have a clue as to what is happening. 

Sounds like a ground or short issue. I'd suspect the wiring harness or damage behind a fuse panel. One of the battery cables usually grounds to the block or frame....it may not be seated 100%. Those are my best guesses. Have you Carfaxed your Sonata?