Occasionally, the transmission slips when moving off from a full stop. It feels like the transmission is in high gear though on one occasion it did this right after backing out of a parking spot, as in it wasn't in high gear to begin with. It doesn't happen all the time and I haven't noticed a pattern for when it occurs. The latest occurrences were 8 days apart (it's a daily driver) which is the shortest interval thus far. The last time it slipped, I shifted to neutral then back to drive while stopped. Drive engaged with the harsh clunk as it always does in the 70K miles I've had the car but still disproportionate power to the wheels considering the revs. I accelerated through the slipping to 40 mph by which time the revs came down to where they normally are. The transmission's been fine since. I'm running B&M Trick Shift synthetic for the past 10K miles or so. The fluid is clean and clear and smells about as it did out of the bottle. The fluid level hasn't changed since it was filled. Do these symptoms ring any bells?

Thanks,
Sixto
87 300D