Tanzen

So I purchased this 2003 Mercedes E320 recently, with roughly 153000 km's on the clock. Since purchase, I have put about 1500km's on it, and I am not too sure if this problem was there when I first got the car, now there is this droning /humming noise coming from what I think is the engine/firewall (not there in P or N only D). Another odd behaviour, is if I drive spiritedly and I let off it kicks down a gear then if I let go of the throttle altogether it feels like it is decelerating. Of the 1500km's I have only had 2 very rough shifts. I drove around my neighbourhood at below 20mph (low rpm) and did not notice anything no jerking as far as I can tell. The car has a Behr rad from what I can tell, it has a wavy style crimp (the crimps themselves are not continuous), looks exactly like the radiator in the first picture in this: thread. What could possibly be going on with my car?

Thank very you for your time and consideration.