AC sometimes doesn't work at slow speed or stopped.
 

I've noticed the AC in my car will sometimes not work when I am in stopped traffic or slow traffic. I can't figure out how to get it to restart. It only seems to start working as soon as the car gets rolling, and even then it requires car getting up to speed. Is this just an engine heat management plan by mini or do I have an issue with compressor not engaging when it should be? At low speed or stopped the compressor is not engaging at all.