Just get up, get out and have a lovely dinner by yourself. I have proudly and happily enjoy dining by myself in restaurants (including fine dining) on six continents.
People are way too concerned with what others think. People actually don't care if you are dining alone so you shouldn't. Bring a book if you are anxious about dining alone. I got over the dining with a book a while ago. Now I enjoy my wine, my food and people watching.
There are so many great restaurants in Berlin, which I have dined in alone, and I hope you experience at least one of them.
BTW, not that it matters but I am female.
Good luck.