Firstly, there are practically no spacious rooms on the ISS where an astronaut may get himself stuck in the middle of the room from where he cannot get to the nearest wall. This is practically impossible if only you are not in the Japanese Experiment Module named Kibo.
But let us imagine that one of the astronauts on the ISS somehow ended up in the center of a spherical room with a radius of 10 meters. Will he be able to get to the wall?
The answer is yes, he can. But for that, he can try some tricks without any help.
Going to Sleep
I know that it sounds funny, but here is what will happen if he gets to sleep somehow in this weird situation. Any inhabited space station is designed in such a way that there is no standing air inside. Otherwise, the astronaut, once in the area of stagnant air, simply risks suffocating and dying from a lack of oxygen. Therefore, the ventilation system at any space station constantly circulates the air so that it does not stagnate.
Therefore, he does not have to do anything. The air currents circulating inside the station for several hours will inevitably move him. He just needs to relax and wait for several hours for the air currents to do their job.
Another weird-sounded method is swimming in the zero gravity, as he can actually float. Of course, this method will only work indoors filled with air.
Unlike swimming in the water, each stroke will move him at a very short distance (a few millimeters), so to overcome 10 meters in such conditions, he should be a very strong swimmer.
Throwing away his clothes
A stuck astronaut can take off his T-shirt, tie it into a knot for convenience and throw it away from himself. According to the law of conservation of momentum, he will be accelerated in the opposite direction. It is unlikely that a one-time throw would be enough. He has to repeat it several times.
It is very important that the direction vector of the throw lay on a straight line passing through the center of mass of the astronaut, otherwise, instead of the desired movement towards the wall, the result of the throw may simply be rotation around its axis.
Blowing air out of the lungs
This method is probably the least effective. It consists of straining the lungs and blowing in the direction opposite to the desired movement. By blowing air, the astronaut will create small traction moving him in the right direction.
As in the previous method, it is very important that the thrust direction vector lies on a straight line passing through the center of mass of the astronaut.