There currently are a variety of options to travel by night train from Wolfsburg (Germany) to Karlsruhe (Germany), taking approximately 6 hours: Namely the ICE 273 and the ICE 2513. These lines are operated by Deutsche Bahn.
Deutsche Bahn (DB) exited the actual night train business in 2016. However, it operates around a dozen Intercity and Eurocity trains that run exclusively at night.
These trains only have first and second class seats. The cars remain lit throughout the night and the seats cannot be reclined.