Isuzu Rodeo A/C blows cold then warm

I have a 2000 Isuzu Rodeo with 230,000 miles. The A/C is cold when first turned on after start up, warm or cold engine. After about 5-8 minutes running on a sunny day, driving or at a stop, it starts blowing warm. If I shut the A/C off and leave it off for 30-45 seconds, it will blow cold again. On an overcast day it will blow cold for 15 minutes or more. This has stumped several technicians already so I am hoping someone here can help. Thank you very much.

The evap coil maybe freezing over due to low charge. The low/high pressure switch maybe cutting it off. With guages on it should not be hard to figure it out.