First thing you have to do is be able to return to a known position on the machine once it has been turned off. You can do this several ways.
You can setup Accurate home switches that allow you to automatically ref home and that would setup the base corrds on the machine the SAME everytime. That way you can return to the exact position on the table when you restart.
You can Manually reference back to a known part of the table or material on startup each time. That provides an exact restart position as well.
NOW you can just write down where you left off (line Number) and then use run from here to return back to that line and restart the cutting.
In a nutshell, (;-) TP