99 cavilier overheating at idle

I ran into a problem of an overheating motor a few days ago. I checked under the hood and notced the fan was not running, I checked the fuse which was good and I switched the relays from the air conditioning and the cooling fan which had no effect (they were the same type of relay) I drove the car home and noticed that at anything over say about 30 MPH the cooling system functions properly and also noticed that when not moving the AC compressor kicks off and the car runs really sluggishly, but when it gets back up to speed the temp returns back to where it should be and everything else functions properly as well, it is a 99 cavilier with a 2.2 L and a 5 speed manual, has about 120K miles. Any help you could offer would be greatly appreciated, thanks a ton!