not starter, starter only works when?? at startup , nothing else.
you are right it could be a ignition coil, but i rarely see these fail, the ones i know fails is the ignitor which is the transistor that triggers your coil from firing the plugs...
when you did the tune up, did you change the cap and the rotor?
does the car runs smoooth when it starts back up? could be a main relay problem too.