If you have the automatic climate control module (11 buttons), then your final stage resistor is starting to fail. Your system may be working today, but tomorrow it will "play games" again.
This resistor is easily replaced and it's $127 CDN at the dealer.
Don't buy a used one as it will end up failing anyway. This is one of the weak points on the E36.
To replace the resistor remove the footwell plastic cover on the driver's side.
Look at the back of the new resistor as the existing one is hard to see when in place, just to the right of the accelerator pedal. Remove the 2 screws and unplug the resistor.
1996 E36 M44 318i 5sp LSD