AC sometimes won't turn on until we hit a bump on 2004 Pontiac Vibe

A quarter of the time we start up the car from sitting in park for more than 2 hours, the AC will not turn on. The dial for the fan is rotated clockwise but the blower will not turn on in either the cool or heat setting. Then within the next few min. when we hit a speed bump or just a bump in normal traffic, the AC comes on.

Any ideas what could be causing this?

Asked by for the 2004 Pontiac Vibe
Sounds like a loose electrical connection in your A/C system. Your A/C system needs Diagnosis, here is an article to help you with that.