I have seen this be attributed to the ignition switch on 123 cars but have yet to see this the culprit on 124's. That doesn't mean that it is not the problem.

Two other things that could be the problem are worn blower motor brushes or a slipping serpentien belt. The 124 has a sensor on the a/c compressor that will shut it down if the belt slips. The way to reset it is to turn off the ignition and restart the engine.

Hope this helps,