Marthese Demicoli

My is Citroen C5 year 2002 The car air conditioner stopped. I cannot find the problem When you put the AC on, you hear compresser starts and the blows start too but it work only for 1 mintures and everything cut off you can switch off sometime yes sometime no. When is no you have switch off the car and start it agian at that time itswitch on and let to swith off. What do you thing the problem is?