I have a 1991 mercedes 300SL with only 63K miles. Some times it will not crank.

What is your question?

Dash lights come on, fan blows, power windows work, but no crank. Then it will always mysteriously works later... Some times minutes, some times hours. Suggestions on possible problem? Sometimes week can use it for weeks with no problem, other times will not crank when attempting to start several times in a given week.

How long has your 1991 Mercedes-Benz 300SL had this problem?

This has been going on since we purchased it last June. Sometimes will go weeks with no occurence, some times several times in a week.