190e Mercedes Benz

Check the exhaust system for restriction, throttle valve switch and airflow sensor-

There are a few things you can do and check on your own;
Have the trouble codes pulled as the Check Engine Light does not have to come on for the computer to give you problem codes that will indicate parts or systems that are nearing a failure by reaching a set value that it has gone over.
Any Advance auto or Auto Zone will do this for free.
Check the intake and exhaust tract for anything impeeding the path. Often old catalytic converters will fail and fall apart and clog inside themsleves impeeding the flow of exhaust and keeping the engine from reving. There are several catalytic converters on your car. Check them by getting under the car, in a safe manner with jack stands holding the vehicle, and bang the converters with your fist or a rubber hammer. Not too hard, and listen for loose material and look at the general condition of the exhaust for rust and rattles that may indicate it needs replacement of the converters. If the outside is rusted the inside of especially a converter will be much much worse as far as corrosion goes. It won't take much loose material to clog up the exhaust either.
Check condition of vacuum hoses and look for vacuum leaks.
Check the igniton system, spark plug wires, spark pulgs, igntion coils, for general condition and if they have never been replaced the plugs and plug wires are something to consider replacing.
The last thing you can check, and this is dependant upon the outcome of the trouble code test as it may lead you to the issue, is to get the fuel pressure checked or check it with a test gauge. You can get test gauges on a loaner basis at Adance Auto and Auto Zone. The test port is on the fuel rail of the car and the kit will come with adpaters to fit it. Let the car sit overnight before attempting this test as the fuel pressure will have time to drop. Do not start the car or even put the ignition in the, "ON" position as this primes the pump and pressure will be back up in a range that can be dangerous to work with. Pressure must be bleed off by a fitting or bymeans of waiting for pressure to drop to make it safe to work with.