A/C Working on and off

1993 Honda Civic LX Automatic Mileage 135000. My A/C cools off when I start the car in the morning. But when you get on the road for like a few minutes, it stops cooling off. You would have to turn the A/C switch off for like for a long time and then then turn back on, so it would cool off again.

What might be the cause of it? And approximately, how much does it cost to fix it?

thank you