The transmission won't shift properly. Why?
on 2007 Mercedes-Benz E320 BLUETEC

Restarting the engine seems to reset the sensor.

It sound like your car may be going in to "limp mode" or limp home mode..This happens when the computer senses something is wrong. I had this problem on my E 320 after hard acceleration. Once I switched off the engine and restarted it things were okay again. The problem was the throttle position sensor and cost about 350 to repair.