My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
This is usually a fault with the window motor being weak or the window guide seal/weather strip worn into by the glass of the window causing the window to bind when rolling up.What happens is once you start to roll it up if it moves slow the control unit detects or thinks something is in the way of rolling it up and causes the window to go back down again or also called pinch protection.
What has to be done from here is to inspect the window guide seal/weather strip for any damage with it needing repaired and if found to be o.k. then the power window motor itself needs replaced as it is weak and isnt able to lift the window properly.
With a weak window motor the window will still roll down correctly but wont roll up properly causing this here.
Being a new model usually you wont see a fault with the window motor but it is possible either the window was installed and adjusted incorrectly damaging the window seal as well as weakening the motor with the seal and motor needing replaced.
This will have to be checked further usually with the door paneling removed to see if seal and/or motor needs replaced.
Being a 2015 model this should be covered under factory warranty at a Mercedes dealer at no charge to you.This is the best thing to do is to have a dealer look into and repair this since it is under warranty.
If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.