If restart turns AC back on then it may be cabin temperature sensors

I had a similar symptom. The blower fan and the controls for the A/C and re-circulate stops operating. If you shut the car off and turn back on it will work for a while.

The problem may be with shorted cabin temperature sensors due to dirt build up. There are about 4 temperature sensors. Two of them are located, each, near the door jams behind handles, inside roof cloth cover. (Other two are inside the vent tunnel behind the dashboard and they may not be as dirty as the other two)

I took them out and cleaned all dirt off of them. I have not have the problem since.

Ronjon
'93 850

Have you ever done the evaporator service? If not, you most likely have the infamous freon leak.

when your a/c shuts down, i assume it's still turned on - look and see if the compressor is still spinning (with engine still running)

if the compressor is not spinning (engine running, a/c switched on) try turning off a/c for 10 minutes, and then turn on again, and see of it works (compressor spinning) - if so, you could bridge the 2 terminals on the pressostat next time the problems occurs, to test the pressostat (this is switch on low pressure a/c line, next to where the a/c pipe comes out of the evaporator on the bulkhead/firewall)

Try searching for posts (my posts) on 'compressor' for more details

Kevin