A/C sometimes won't blow cold air. on 1994 Mercedes-Benz SL500

Sometimes if I simply turn the car off and then back on it starts blowing cold again.
At time it may take a week to 10 days for it to start working again & it will work fine for 2-4 weeks. What could this be? it seems like a switch.

Asked by for the 1994 Mercedes-Benz SL500
Mine was doing the same thing.turned out it was the blower regulator and blower motor that kept shorting out.Cost me $1500.00 to get it fixed.