New noise, just started (car is 85, 190E 2.3, 130K miles) - when the engine is on and the car in park, there's a humming/grinding/chirping noise from the bottom, rear of the car. If you switch the car off, then bring the ignition to "ON" position (without cranking), it makes a loud noise (same type) for a split second, then no noise. Then when you start the car, the same noise starts again from the bottom rear.

What could it be? I am going to the tech after 2-3 days anyway - could it be something urgent, or can it wait a couple of days?

Thanks a lot.