My old Ford Explorer always shakes at idle but it smooths out past 100 RPM. I've changed sparkplugs, cleaned the MAF and throttle body. The engine is in good shape and never burns oil. 4.0 L V6 with 186,000 miles.
The main thing on those things when they do this, you should try the obvious. A lot of them get an intake manifold vacuum leaks. It’s a very common problem on those vehicles. Of course, always check the motor mounts, too. They can be cracked or something like that. But, a lot of times, it’s the leaking intake manifold gaskets on that. And it is a pretty big job. If you are not up to it, get in touch with YourMechanic. They’ll be able to diagnose your car’s shaking and idling issue and repair or replace your intake manifold gasket if necessary.