the engine mounts could be bad
You rotors are warped and will need replaced/resurfaced.
it could be that you need an alignment on the wheels.
crank sensor wire probable it's making contact with some ground check all the sensor wires with de engine on and shake them carefully
My Dodge Charger doesn't shake...
The engine management system may not be adjusting for the extra load of the A/C. Can also be the A/C compressor is seizing up. Have this looked at by a professional.
it will shake uncontrolabley
The car is stalling for a mechanical reason possibly engine overheating theyres no reason it should naturally cut off...unless the engine is too hot and its protecting itself.it could also shake if its low on gas...my 1989 dodge spirit shakes when low on gas and jerks
Your rotors need to be turned. They have become warped.
Who checked them and how were they checked? Pulsing ONLY when you use the brakes is just about always the rotors. You might want to check for a bent wheel, but that would be an almost constant vibration.
bad engine mounts
My 92 PA had a similar problem. At low engine speeds it would shake pretty bad. It turned out to be the harmonic balancer. You can easily check this by looking at the front end of the engine. It is the pulley that drives all the belts. If the rubber has deteriorated, it could be the cause of your problem.
Miss or vacuum leak.