Starter or solenoid
 

Maybe neither. i would take the solenoid cap off the main cannister and
see if the contacts are corroded. and checkfor wear. sometimes jsut a
wipe down to knock off the "green stuff" will do the job. Plush you
need to pop off the end cap of the starter motor and see if the brush
holders have been rusted due to humidity. and see if they move freely.
if not. a good dose of penetrant will usually free them up.

also see if the drive clutch needs some oil on the shaft to allow it to
move freely and engage smoothly.

Tim