Thank you very much for asking. There are bus stops in San Niclà and in Sclamischot. Just take the public bus getting back to your car. For travel times, we recommend the SBB online timetable: https://www.sbb.ch/en/timetable.html
There is also a connection from Sent, but here you have to change in Scuol. If you have any further questions, please do not hesitate to contact us. We wish you a lovely time in the lower Engadine.
Best regards, your destination Engadin Samnaun Val Müstair