Specifically, the restart file contains coordinates, delta coordinates, velocities, integrator state information, etc. A binary trajectory file, sometimes called a 'dcd' file by people with limited CHARMM experience (I use .trj extension), contains only coordinates.

You can get a restart file (I use .res, but the extension is irrelevant) after the dynamics run since that's when it is normally written, but the proper DYNAmics setup is required; OPEN the file, and point to the integer unit number via the 'IUNWRI integer' option.

In summary, it cannot be done from just coordinates, and the best advice is still to repeat the initial run with the correct setup.