DSG or DMF problem developing

A couple of time recently I have started my 07, 140 BKD, DSG and driven a mile or so. Then stopped at the lights only for the engine to die after a few seconds (in D with foot on brake). On other occasions driving along the motorway at between 60 -70 on light throttle I get a loud rumble like driving over ridged concrete, coupled with a low vibration feeling in the car. If I apply the brakes I get an increase in the vibration and rumbling. Then if I slow down to say 50 and back up to 70 everything is normal. No vibration or rumble? Gear changes up and down are smooth.

So could this be the DMF messing around or a problem with the DSG?