Hi, I rent my cosy and quiet flat (rear house / backyard) from time to time when I work abroad for a couple of weeks. It is located in a pretty popular neighborhood of Berlin, close to the Tempelhofer Feld (former airport, now giant park). Stepping out the door, you'll find quite many bars, restaurants, small shops, a bi-weekly market & a nice atmosphere.
I do keep some of my personal stuff in the flat (e.g. books, cosmetics...) but you'll have an own wardrobe and enough space for your things.
The Metro Station "Leinestraße" (U8) is only 100m down the street. The U8 takes you to many central places, like to Alexanderplatz in only 13 minutes.