It turns out that yes, there are things you can do, but they depend on things other than the astronaut's body, and they will take a long time.
Physics tells us that an object's translational momentum is constant unless acted upon by an external force. If the astronaut's net momentum with respect to the room is zero, there is nothing they can do to start their center of mass (which includes any clothes or other things they might have with them) moving in some direction. That would require a non-zero momentum, and the only way to accelerate their center of mass is to have some external force act on them.
However, one could eject part of the "system"—the astronaut and the things they carry with them—in one direction, giving it some non-zero momentum. To maintain the zero-momentum state of the system's center of mass, the rest of the system has to have the same magnitude of momentum, but in the opposite direction. The principle is the same as a rocket engine. The example often used is for the stranded astronaut to remove a shoe and throw it in a direction opposite the direction they want to move. They will then drift in the direction opposite the shoe's path—probably spinning as well.
But they'll be drifting slowly. The magnitude of an object's momentum is just the mass of the object times its velocity. Say the shoe has a mass of 1/2 kg and is thrown at 10 m/s (hopefully with no critical station components in its path!); its momentum is 5 kg-m/s. Assume the astronaut has a mass of 50 kg. For her momentum to be 5 kg-m/s, her velocity must be 0.1 m/s. If the wall is 10 m away, it will take 100 s to get there. That is, assuming no air drag.
When you consider the air in the big room things change somewhat. The thrown shoe starts the astronaut out at 0.1 m/s, but air drag slows that speed as the astronaut moves, so it takes longer than 100 s to get to the wall. I'll say more about the air later.
If the astronaut is barefoot, and carries only very lightweight items (wearing only a swimsuit? and carrying only the key to a locker?), the time to get to the wall will increase dramatically. Assuming the astronaut doesn't want to part with any essential clothing, throwing the key is the only option.
But there is a limit to how fast you can throw light items. Having a 20-gram key doesn't mean you can throw it 25 times faster than the shoe to get the same momentum. Unless this astronaut is also a baseball pitcher, they might get a 20 m/s throw, for a momentum of 0.4 kg-m/s, and a velocity toward the wall of only 0.8 cm/s—1250 s to the wall!
Back to the air. You could actually do swimming-like arm/hand motions, propelling air with cupped hands, and gain a little momentum. But the mass of air moved is really small, so it would take a long time to get to the wall. Air movements due to ventilation would probably move you faster, as the Skylab astronauts found. Without the air, this technique wouldn't work at all. So if the room is evacuated, and you're in a space suit with nothing to throw, you're up the creek without a paddle. I think this version of the answer is closest to what you're looking for. There is no combination of body movements that, without any kind of aerodynamic effect or throwing off items, would impart momentum to you. If you're in a space suit, you might be able to vent some of your suit air, but you won't get much speed out of that.
So, a couple of good rules for when you're in a spacious space station: 1) don't go barefoot; and 2) carry a sturdy water bottle with 1-2 liters of water. Of course it's handy to have water to drink, but 2 liters is a lot; however, having 2 kg of water to toss gets you to the wall faster. Make that water bottle sturdy but flexible, so you don't dent walls or equipment.