A standard ticket will allow you to stop along the way as much as you want to within the validity period. However, those are expensive. IIRC Berlin-Munich on the ICE is around 120 Euros. Advance purchase tickets can be as low as 39 Euros on the same journey. I know that you can do up to 2 stopovers (max 48 hours each) on an international ticket for the lowest priced tickets between start and finish. I often snag a 39 Euro ticket Berlin-Prague-Vienna. This can be done online at db.de. However, I'm not sure if this also applies to domestic tickets. One helpful tip: it is also possible to get a cheaper ticket (for travel only within Germany) by purchasing an international ticket.

For example: going from Berlin to Munich. You might find a cheaper ticket going from Berlin to Innsbruck via Munich, than an actual ticket Berlin to Munich. You just have to make sure that the train you're booking is going that way. It also works if you're going to Basel or Zurich from somewhere in Germany, and you only want to go to Stuttgart or Freiburg. Another hint: Austria's oebb.at website often sells the exact same train ticket cheaper than what Deutsche Bahn is selling for the same specific train.