92 500SL won't start, starter doesn't turn

[carldowning]

This isn't a new problem, battery is good everything lights up,just no cranking. The car did this for a week or so then started fine for a month. Now nothing. Tried starting in neutral and moving through the gears to test the Neutral safety switch, moved the steering column up and down to see if ignition switch was shorting, both did not produce any results. How can I logically track the power to the starter and how do you access the starter if need be? Thanks