Any decent mechanic can remove, clean, and tighten the battery cables. You may have a corroded battery clamp that needs to be replaced, that can prevent effective tightening of the clamp.
One other possibility is that your starter solenoid contacts are worn, which results in an intermittant no start. Had that happen to my '96, to fix it I removed the starter and replaced the contacts. Has the starter ever been replaced?
But check the battery connections first.