The RPMs are really low, and the engine is shaking.
It sounds as though you may have a vacuum leak. A vacuum leak is simply unmetered air that is allowed to enter the engine and disrupt the air/fuel ratio. This can cause many symptoms including a rough, low idle. There are a handful of methods used to locate vacuum leaks. The best method, which professionals use, is a smoke machine. The machine is hooked up to a vacuum port and forces smoke throughout the system. Smoke can be found escaping from the location of the leak. I suggest having a professional inspect your vehicle firsthand with dedicated equipment to diagnose your vehicle’s low RPM and vibrating issue and determine what repairs are appropriate.