I am having a problem with my starter.

It will engage but disengage before starting the engine and "whirring" to a stop. It always does this now if I try to start it right after the glow plug light goes off. For the last few weeks it would only occasionally do it. Sometimes it would intermittently engage and kick out but the engine would still start.

Here's the kicker:

If I wait about 15-20 seconds after the glow plug light goes off it will fire up perfectly with no kicking out.

What would cause this?

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1993 W124 300D
-297K on the clock as I type this.