When it cools off it comes on until it warms up again.
My AC is cold but after it is run for about 10 minutes the compressor shuts off. on 2000 Mercury Mountaineer
Time for a compressor, accumulator, orifice tube and flush the condenser. You have a restricted o-tube.
Or a faulty evaporator thermister or a faulty pressure swich or a stuck clutch relay causing it to stay on till pressure gets to high and cuts it off as a fail-safe.or get it diagnosed at a shop you trust (I hope you did the last item first!).