You need to add a lead in and a lead out to the toolpath. Basically what this amounts to, is parking the tool at a start point such that the outside of the tool is tangent to the actual profile of your part. Then, command a feed move from that point, to the profile, while invoking G41 or G42 to call up machine compensation. You will need a radius or diameter value inserted into your controller's tool diameter table.
I don't use Mastercam, but there should be a setting in there for the lead in and lead out, at least now you have half an idea what you are looking for, maybe you'll know it when you see it