2003 Dodge Dakota Hesitates terribly

I can be sitting at a stop sign and the truck starts idling rough and I start off it backfires and jerks and sputters for about 50 yards.....It sometimes will recover and sometimes not. I have found that if I turn the engine off and back on the problem is gone. It will go on perfectly until I have to sit idling at a light or stop sign. It does not always happen, however the longer I sit idling the surer the chances are that it will act up. It does not matter if it has been driven a lot or if it is just starting out....it is so random it is pathetic. I take it to the mechanic and it will not do it. While it is random it is guaranteed to happen when there are lots of cars behind me in rush hour traffic or if I am pulling on to a busy highway....the most inconvenient and embarrassing times. I have had catalytic combustors put on, O2 sensors and many small things. Can't get it to stop.