I hear the six speed box casing is a bit on the small side for what it contains so the lubricant capacity is not that large. So only once the car starts moving, the gears are then properly lubricated and changes are easier then. This condition gets worse with age and mileage.
My 2.0 6 speed is also notchy when the oil is cold.
Once it warms up a bit better, it’s untouched.: