The 27-year-old, plus-fours wearing Swede is seeking his first European tour title and his second-round 66, which included two eagles and four birdies, put him in a good position heading into the weeken.
Two shots behind were first-round leader Fabrizio Zanotti from Paraguay, Irishman Paul McGinley, and English duo Danny Willett and Chris Wood.
"Now I saw that I'm up there, and of course it's going to be a new situation for me," said Sjoholm.
"But then I watched a lot of Euro Cup the last two or three weekends, I've seen what happens after four or five minutes, and I'm happy to be on top at the moment - but I would rather be on top on Sunday.
"I'm just enjoying this so much, I don't really think too much about it. It's just a great feeling and a fantastic tournament. I've always played here in Germany, and it was good to play well at the new venue."