# C, 65 bytes

    t;f(char*s){for(;*s;)*++s-32&&*s||(t=s[-1],s[-1]=s[-2],s[-2]=t);}

[Try it online!](https://tio.run/##XVHLbsMgELzzFStXSYwfVeumvVBHitRWPeQU5VKlOVg2tlEJWIDlQ@Jvd8Gp8ugKodXM7DBAHld5PgyGlH5eZyrQ@FBK5ZNAExyEoY6fkuk00Mejb1K9jR930bi7Phn7ZJcaTPrhjomctwWFV20KJu/rBUJMGNhnTPgYHRDYckeANmqbPL/syAh1NeMU/LKiRvuWisByETgTgfEoOc26coYcUmfBqXByTG5Iacn5/Aorwam23GaGNIXZt5jhM3sxdnXRwQO5YcJQXoD@3DXKHln63kTDJNDgudQ2v4x5BF688K6ylf@yNu3ptn9Qj/phU2dC/6Av2VIFHeW5pHu0qZkGuzIBWdNwij44axpWCVhRY6hWsFSyLQQynxTkW2FfeLni74JW0LHagO7smP0UPqrXvw)