1992 Toyota Camry Extreme Vibration

Car starts with no problem and than at random intervals the engine starts shaking violently. I step off the gas the shaking stops and the car drives normally until it starts up again. It could be 3 minutes it could be 15 minutes but it does come back. The issue can happen with a cold engine or hot. Taking my foot off the gas alleviates the issue.
The timing belt was changed at 100k and new plugs.
It almost feels like a badly timed engine. I hear no misfires.

In neutral or park engine runs smoothly. I can throttle up and engine responds. While driving when engine began to vibrate I shifted into neutral and vibration continued. I proceeded to gun engine and the rpm's climbed smoothly up and down. The vibration continued regardless of what the engine was doing even though it feels like the engine is at fault.

I drove the car yesterday to and from work a total of 40 miles without incident. Next day I go to work and the shaking started all over again.

No check engine light