Car Stall problems of the 2017 Mercedes Benz C300

When the car is in the a feature, where it turns on and off when not in motion, it gets stuck in that mode as if a magnet is holding it in that position. It will not move, it stalls. I turn it off and turn it back on and sometimes it still will not move, sometimes, it will not turn back on. This has happened on several different occasions. Once, I pulled to the side of my mailbox to pick up mail, and another occasion I pulled into my garage, and it stopped, and would not turn on. This is very dangerous, I would hate to be in traffic, railway crossing, ir stop sign and this occurred. Peoples lives have been lost due to this issue. One lady was hit by a train when this same situation occurred and lost her life. I am very concerned for my safety and of my grandkids whom I transport in this car. It also seems that something is wrong with the gears. Sometimes, I put it in reverse and it sits there. I put it in drive and it will not move. I feel very unsafe in this vehicle. Please help.