starter engagement

[70Custom10Nut]

I just bought a tilt column off e-bay in December and of course after cleaning it up and painting it, I put it in my truck. Everything works fine except for one thing. Sometimes when I'm shifting back into park, the starter engages for a second when the indicator is near reverse. It doesn't do it all the time and as soon as it is in park it stops. Has anyone out there had the same issue? Is it something I did when I put it in? Do I just need to make a linkage adjustment? With the ignition switch on the dash how is it possible for the shift linkage to effect the starter. I really hoping my only ever e-bay purchase is NOT the culprit somehow.