My AC runs fine but it shakes every 30-40 seconds when the car is not moving. Can anyone help me identify the issue?

 

Your A/C is probably low on charge causing the compressor to work harder. The compressor is on the passenger side and can produce some vibrations. There is also an engine mount near it that can become damaged and allow extra vibrations. Best thing is to get the A/C serviced and then to have them check the condition of the side mount.

 

Have it checked out. Sounds like you may be low on freon. Don't add it yourself because if you add too much it will get warm air instead or cold.