My car dies when its at a complete stop

My car dies when its at a complete stop. It wont do it every time either its about 4/10 times itll just die at a stoplight and I put it in park and start it and it turns over just fine and I can drive until it has that problem again. Also it is spiratically turning my instrument cluster on the dash on and off. When that happens with the instruments my radio will lose power too ocasionally. I just got a new timing belt power steering belt and alternator belt. I also had a new wiring harness for my transmission installed. It isnt throwing any codes or error lights either.