My a/c is acting up intermittently. After the car sits for a while in unbearably hot conditions, i start the car up, turn on the a/c (auto) and get warm air...even after several minutes. i can turn the car off, restart and the a/c then blows cold air. any ideas? a couple of months ago i briefly (maybe twice) had the flashing a/c lights on startup. its been several months since that last happened. the start/ restart issue happens once or twice a week, and is always remedied by shutting off the car and restarting. thanks in advance___mark.