That is a difficult question to answer because "German nationalism" isn't easily defined and the term nationalism was indeed loaded so negatively that it was commonly used as an insult thrown between the two resultant Germanies. West Germany was lambasted for not recognizing East Germany or even the loss of land to Poland and to Czechoslovakia. It has moreover retained the nazi era anthem leaving just the "Deutschland, Deutschland über alles" stanza on the cutting floor.

East Germany was, in turn, criticized for retaining the goose step and other "Prussian traditions".

Source: Routledge Encyclopedia of Contemporary German Culture edited by John Sandford

Both countries were extraordinarily critical towards the Jewish state.

According to the BBC polls the stance towards Israel in Germany is significantly worse than, say, in Poland, Italy, the USA or even Pakistan. This might be both a separate autochtonous antisemitic tradition or a product of the Oil Crisis era New Left, since certain other countries - France, the United Kingdom and Spain - share this peculiarity.

A particularly post-war German antisemite quip is, of course, that the Germans "should stop being afraid to speak their mind about the Jews". Last time it made the rounds around the world in the «What must be said» poem by Günther Grass. But it has been around since the first Arabic-Israeli war. The entire German press and the German government have been savagely critical of the Eichmann trial and yet every single author was pretending he was some taboo-breaking rebel.

source: «Der Eichmann-Prozess in der deutschen Presse» by Peter Krause

Konrad Adenauer believed in a powerful Jewish conspiracy in the United States and there's still some genuine interest for borderline-antisemitic literature. «the 200 years together» by Solzhenytsin was not published in English but there is a German translation; books by Mearsheimer and Finkelstein are extremely popular, as well. Thilo Sarrazin is a former social democrat politician and member of the central bank whose racist diatribe against the Turkish minority became a best seller in Germany. Still the term "nationalist" is usually reserved for the parties on the extreme right like the NPD (old right) or the Republikaner (new right).

The NSU is a nationalist terrorist gang caught by the police after a botched bank robbery. Since it was discovered the state security was well informed about and partly involved in their activities there was a major public scandal and a successive parliamentary inquiry.

The public display of German flags is another thing done as long as there's a Federal Republic of Germany and yet claimed to break some supposed taboo on German patriotism during each new football championship.

edit: another thing worth of mention are the German nationalist student fraternities - the Burschenschaften. They had been banned in the GDR and there have been some calls to ban them in West Germany as well. They've been around since the Napoleonic era and were the first to use the current German flag.