Many german surnames have their origins dating back to the Germanic middle ages. The name German, like many other nationalities no doubt follow this same evolution. This doesn't make pronunciation of name german or even baby names German any easier. But at least there's an historical context to place your lack of diction skills. The process of forming German family names began around the year 1100 and extended through 1600. The development of name German owed everything to a person's social class and demographics. For example, first names identified specific persons. Over time the first name began to be applied to the bearer's whole family.
If you know a little German, you will obviously have more luck with the language and diction in general. Certainly you will be able to recognize name German more easily. If you're like me, and have no grasp of the German language, at least you can look for several language clues to help you on your way.
Regarding German surnames, look for names which begin with sch. In English this sound is best represented by sh, like in "shine". You can easily then pronounce names like Schaefer (Schafer), Schmid (Schmitt), Schneider, Schrader, Schroeder, and Schultz (Schulz), just to name a few.
Names with ei are mostly German (although there are exceptions): for example Reichmann, Reimann, Reimers, Klein, and Weiss.
If a name ends in -mann, -burg, -lich, or -stein, it's a likely indication that the name is German. But in certain settlement areas -- again we're talking geographics and demographics - those same endings could also refer to Swedish and Russian Jewish backgrounds.
I have always found the German language to be the least attractive in terms of sound. That is -- how it sounds rolling off my lips. Names like Bruno, Dieter, Dietmar, Friedrich and Fritz are somewhat intimidating to me. They are cold names. Name German that recount images of people working in coal mines or steel mills or worse. Name german for females are not much better: Berta, Brunhilde, Elfrieda, Gertrud, and Helga for example. These names do not conjure up images of forest nymphs splish-splashing in a pond somewhere. I'm convinced that a name makes the person and not the other way around. With cold german surnames or baby names German like those mentioned above, I believe a person creates a persona that is inescapable.
Take the name german Adolph for example. It's no secret that Adolph Hitler yearned to be an artist as a youth. Perhaps world history might be completely different if Adolph's art instructors had liked his artwork and spurred him on in the field of graphic design or whatever. As it stands -- for whatever reason -- Adolph just isn't a name German of an artist. It's a name of a dictator and is forever linked with that image in mind.
Like any nationality, the names and language are specific to the region. Every culture is ego-centric to a certain degree. So while I don't particularly find any german surnames to my liking or even the entire language for that matter, there are plenty of Germans who probably don't enjoy pronouncing western languages. English and American for example. The diction, tenor and timber of the words are completely different. In this I take some solace, because I know that my German counterparts are having just as much of a struggle as I have.