Mysterious Shaking

I have a 98 Toyota Avalon with 85K miles. A few years ago I hit a pot hole with some force and it caused the car to start shaking. I let it rest for 10 minutes and the shaking went away. Since then, it’ll shake every once in a while. When it’s happening it will be very noticeable when I’m standing at a stop or driving at low speeds. If I speed up, then I do not feel the shaking. I usually just pull over and let the car rest for about 15 minutes and the shaking goes away. The mechanic could not diagnose since the problem can’t be duplicated.

Has anyone checked the motor mounts?

Not that I know of. I don’t know much about fixing cars, but if the motor mounts were bad, would the problem be sporadic?

Possibly