Car shakes when idling' - 2000 Chevrolet Cavalier

Well this could be caused by a number of things. But the most common cause is an "engine miss." You could have 1 cylinder that has stopped firing. This will cause a very rough idle and very possibly shake or shudder whenever you accelerate. Another cause may be a main "vacuum hose could be disconnected" from it's port. Vacuum leaks cause engine shake at idle. Check for loose, cracked, or disconnected vacuum hoses under the hood. The third and least likely cause is a "broken or worn motor mount". If the engine is not securely held down in place by all the motor mounts, it will vibrate excessively and cause a shake at idle. The engine miss and motor mount problems are 2 issues best left to a professional to tackle. But as I said, you could tackle the vacuum leak issue yourself by checking under the hood. Hope this helps, good luck!