Are you saying that after you loose cooling you can get it back by cycling the ignition key?
If so I would look to your belt tentioner. The comparative judgement, that disconnects the clutch on seeing different compressor vrs engine speed, only resets by cycling the key. In other words, if your belt flops and the compressor slows briefly, the compressor is shut-off until the key is turned off and then back on again.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician