1996 Geo Prizm Engine vibration

When I start my 96 Geo Prizm car when its cold, there is alot of what seems to be engine vibration, felt inside the car during high engine idle. The idle drops in speed to around 1000 RPM, once the car is fully warmed up in about 15 minutes. And then eventually drop to around 700 RPM after another 5 or 10 minutes. At 700 RPM, the engine quiets, and the loud engine vibration is gone.
Same thing when driving, if I do not let the car warm up for 15 to 20 minutes, I feel alot of vibration in the cab when I drive, until the Idle drops to 700 RPM and then it drives perfectly fine. I had the motor mounts checked, I was told they are worn - but seem to be ok.

My main concern is Engine Vibration - it is strong enough to make the hood and front fenders vibrate to the noise of the engine when warming up, then its fine!

Sensor check showed all sensors working!

I changed wires, spark plugs, and rotor cap/button.

I'm at my whits end to trying to resolve this - having several day - here and there - trying to figure it out!

Trying to avoid going to a costly repair shop - any solid advice would certainly be most helpful!

Thanks!