This is a common problem. You have a faulty high temperature cutout switch in your compressor. This switch was designed to turn off the compressor if it overheated. This switch can't be replaced (I was told)and you must replace your compressor @ $800+. I have a 1999 S70 and this condition has gotten worse. This "cutout" for 5 minutes would only occure when the outside temperature was over 90 degrees F. That only occured a couple days a year here in Cleveland. Thinking back I know my A/C cut out when the car was new however it never happened very often so I forgot about it. I read somewhere that Volvo techs in warm climate countries have found a way to disable the high temperature switch in the compressor. I am going to experiment this week by releasing some regrigerant from the system and refilling it with an R-134 Oil Charge to see if the additional lubricant makes the compressor run cooler.