Auto gear transmission not engaging in gear, unless restart

[Hash1]

W204 c220 2012

Auto gearbox, gear wont engage in D Or R, car wont move, unless a restart of engine. Then everything is fine. Gears change very smooth and no issues.

Any ideas? I think transmission been serviced as the gears change silky smooth first thing on a cold morning.

 

[ajlsl600]

Something to do with key switch unit not talking to shifter unit or vv. Vaguely recall possibilities of brake switch playing up someone likely to be along