I have a 2005 Focus - had the same problem.
It is a connection problem, mine just happened to be that the negative side of the battery (the post) was corroded (a lot of white chalky substance on it). Cleaned it off with 1/3 cup baking soda, 2/3 cup water and wire brushed it, dryed it off, reconnected, and put battery post gel all over it. No problems since. You say Autozone checked the starter, alternator, etc, but did they check the connection to the starter? It has to be very clean and tight. I had that problem also. Hope this helps.
Saturday, January 20th, 2007 AT 2:25 PM