I just read the last fellow that had the same problem with a spinning starter and all he had a bad connection at his battery. I think the combination of a cold stiff engine and a slow cranking starter could cause the sprag to slip into a kind of neutral position (I've never seen it). This was the only explanation we could think of the last time it happened.
Check your battery connections, then check the battery. Look for the simple things first.
Read
This Thread
