A/C has low airflow after driving

I have an unusual problem with my car's A/C unit. It works just fine but after one to two hours of continuous driving with A/C switched on, the air from the vent seems to be restricted. Even when switched to full speed, I can hear the blower's usual noisy sound but the air from it is minimal, at times even worse than minimal setting of 1.

I can solve this by temporarily switching off the A/C unit (set to slower blower speed but with the compressor switched off). After about two or three minutes, I can feel the air from the A/C to be stronger again (just like normal), switch the compressor back on and everything will be as normal. For may be half an hour then the air gets restricted again. I will have to go through the cycle of switching off the compressor and so on.

Do you have any idea what is wrong with my car? My car is now seven years old, never had its air conditioning unit serviced or gas recharged. Could this be from low refrigerant levels?

my car did undergo a major breakdown last year, the car main fan failed and caused the car to overheat and breakdown. The engine coolant leaked into the engine chamber resulting in a very expensive overhaul to the engine, replacement of the water pump, rubber hoses (cracked).

Any assistance is greatly appreciated.
If you need more information please let me know.