2002 Subaru Outback Intermittent AC problems

Hi, Just purchase used 2002 Subaru Outback LLBean limited edition yesterday. Only to go about today traveling locally and highway to have the AC stop working and suddenly blowing warm air. Oddly when we turn off the car and restart the car the ac kicks in for about 10 minutes and stops again. I have read that some other people have encountered same problem as this. I am curious if you have heard of any permanent solutions or am I in trouble for the long haul. I just purchased the vehicle last night and no warranty is provided. Scary that the techs didn't see this problem or did they? Or did someone overfill the system so it would mask a possible leak. Please help I am need of professional advice asap as time is of the most important. Thank you!