Hello.
I had a similar problem with my 1997 Boxster on a ferry boat...
The starter was rebuilt for $120 and I also change the ignition switch ($20)
at the same time. These repairs solved my problem.
The starter or the switches are not a big deal to remove and they are
made with Bosh standard parts for solenoid and standard bendix.
Look at this DIY
Starter DIY
Good luck.
