The travel section of the NY Times has, for years, had a series "36 hours in XYZ", describing ways to enjoy a weekend in a city. Arrival Friday afternoon, departure Sunday late morning.
I have, to the best of my recollection, never spent a night in Bern, just a few day trips, so I cannot really make any comments on their
36 Hours in Bern, Switzerland. I hope it may be of some use to anyone planning a weekend there!