The pilot of the multiengine airplane reported that, he had preflighted the airplane about 2 hours before his intended departure and asked ground crew to reposition the airplane. When the pilot was ready for departure, he reported that he did not do another preflight, but only walked around the nose of the airplane to get to the entrance door. After he started both engines, the airplane would not taxi forward. The pilot reported that he thought that he set the brakes, reduced both engines to an idle power setting, and exited the airplane. The pilot observed a chock on the airplane’s nosewheel, and after he removed the chock, the airplane began to move forward. He attempted to reboard the unoccupied airplane, however, was unable to and the airplane subsequently collided with a hangar. The airplane sustained substantial damage to the fuselage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.