After your time in Bern, your next stop is in Mürren, Switzerland. Take the train to Interlaken, and change trains to Lauterbrunnen. This trip takes about 2 hours. When you arrive in Lauterbrunnen, walk across the street to the Cable Car station (you'll see it when you arrive there), walk up the stairs and board the next car. The Cable Car will take you to Grütschalp (about 20 minutes). When you arrive at the top, board the small BLM mountain railway which will be waiting. The ride to Mürren will be another 20 minutes or so, and you'll arrive in the station of this very small town without car traffic.
For Mürren it's probably best to make a hotel-reservation a few days in advance. The best place in town is the Eiger-Hotel right next to the train station in Mürren. However, Hotel Bellevue and Hotel Alpenruh are nice too and a bit cheaper. Make sure you get a room with a view- and when making reservations on the web, make double-sure the hotel you're booking is actually in Muerren.
Remember this is a vehicle-free place, however, most Hotels will pick up your luggage from the train station with golf-cart like vehicles. Just get their mobile phone number or email ahead of time, and text them when you get on the Gondola. They will be waiting for your luggage at the Mürren train station.