a/c wont start, when finally starts it only blows air, not hot nor cold. on 2000 Mercedes-Benz C280

the on/off control does not start a/c, but if i hit a bump or sudden movement, it will start blowing air, just air. not hot nor cold

Asked by for the 2000 Mercedes-Benz C280
Sounds like you're talking about the blower works when hitting a bump; With no cold air it sounds like your A/C is not working at all. Look at the front of the compressor when A/C is on. The pulleys are turning, but is the front hub of the compressor turning with the speed of the belts/pulley.