shim the starter?

[cheatham]

Last winter my starter was having some trouble turning the engine over. I would hit the ignition switch and the starter would whine, but not crank the engine (intermittenly, and especially when the engine is cold- but sometimes when warm). Well after a couple of trys it always turns the engine over. During the summer it did this very rarely and i forgot about it. Now it is getting cooler again and the problem has returned frequently.

Anyone know for sure what the problem is, I would like to know before shim the starter if that will help. I thought teeth might be broken, but the fact that it is 'almost' always happening when cold has made me suspect of that.

Any help is appreciated greatly.

JP