strange crunching with the brakes

[Cliffjohnson]

I have a 2007 ML 280 diesel 3 ltr V6 it has the gear paddles as well as the normal Colom auto shift, over the last 6 months the brakes seem to come on now and again just when you go to pull off, I took the car in to the garage and they said it was a faulty abs sensor and changed it, the car was fine for a month and then it happened again, sounded like the parking brake shoes had failed, I had new discs and callipers hand brake cables and brake pipes, car ok for a month then coming off the motorway got to the bottom of the slip road again total lockup ? managed to limp to the side of the road, now when you switch off the engine and restart hy presto the dam thing works take it to the garage and tell them what has happened !! after a lot of head scratching and blank look no one knows as it shows no faults and it drives on, so just drove up from Devon to the midlands, stopped and some road works dam car brakes lock up again, on with the hazard lights switch off the engine restart and all ok for ?? Please Please, anyone any ideas.