Car vibrating while idling

engine mounts are bad

go to your mechanic

Duplicate question.

When you are in gear at idle with your foot on the clutch you have placed an axial load on the crank which is pushed forward in the main bearings against a thrust bearing. I suspect a failing thrust face on this bearing as it only works under a clutch release load. The only other point that is under load is the clutch throw out bearing but if that is failing you should be hearing a tinny type of rattle when you have the foot on the clutch

if the car is running does it have the check engine light on? if yes what is the code if no then check to see if temp sensor is reading the right temp by plugging in a scanner that can read all data to give you an accurate reading... if it reads wrong temp it can cause running issues

You will have to replace ALL the motor and tranny mounts in a specific order.

If your engine is not misfiring but it vibrates too much while idling your motor mounts might be getting worn out. I had a Nissan with bad motor mounts. I was ok in park but when you put it in gear it vibrated a lot. It smoothed right out as soon as you started moving.

Have you tried checking the exhaust heatshields?

ck for vacuum leak associated with brake booster

The problem is the torque converter solenoid. I had it happen on my 94 Cavalier a few years back and was a cheap fix at the local car mechanic. What happens is the transmission warms up and hits a certain speed where the solenoid engages, but then it sticks and won't disengage until it cools down sufficiently. When it sticks, it causes the car to shake when slowing down and will snub out the engine if you come to a stop.