Volvo: Car does not always start, component failure, sand paper

Question
I own a 1988 240 Volvo.  Recently it has not been starting.  One day it will start next day it doesn't.  I'm assuming something electrical.

Please point me in a direction.  Wiring, component failure ?

Thank you

Answer
Most of the time, corrosion develops on the 12 V contacts on the coil.  They are bare connectors, and when rust develops, it distrupts the circuit in random ways.  Disconnecting those and running sand paper over the metal usually fixes the problem.  Good luck!