2003 Mercury Sable Electrical Problem?

I drive a 2003 Mercury Sable with 62000 miles and from time to time it will just cut off.
Sometimes while I am driving, speed does not matter, you will fell it hesitate, the lights on the dash board will light up the radio will cut off, rpm and speed indicators will jump. This hesitation/interruption is so quick that the vehicle will not quite while driving, unless I am slowing down or at a complete stop at a traffic light. The check engine light never stays illuminated after this happens. I have had a mechanic hook it up to a computer and drive around and when the hesitation/interruption happens the computer will not read a code problem. Any thoughts?

Thanks,
Concerned Driver