I am not sure if I need a new battery, starter, or some elbow grease cleanup/lube. The starter on my new Rockster only engages some of the time. Is this a 'clean it up and re-lube the drive' fix, or am I in for some new parts?

My boat starter did the same thing and a lot of WD40 and physical work cleaned out the dried grease and grit that was hindering the engagement. Can I be that lucky twice?