Vintage Cars: 83 Mercedes 380sl starts then doesnt, mercedes 380sl, starter selenoid

Question
it's pot luck when you turn the ignition. sometimes it will start and run great. then you shut it off and it won't start.

Answer
sounds like   a ground or starter issue.  Clean all wire connections in starter circuit including those on battery and starter/selenoid.  Could be a starter issue, next time is does not start hit starter with hammer and see if she starts then - that would point to starter.  Could also be in ignition switch ...  try this stuff first