Todd
I had the same problem a couple of summers ago,  occasionally the starter would not engage even though the battery was charged.  I took the starter out and cleaned up the solenoid, I also replaced a small pivot pin that was badly worn, since then the starter has worked fine.
George 
'85 Westfalia

>>Can I just take the solenoid out and clean it? Or is this >>just the
>>beginning of starter failure? battery failure?