I have exactly the same problem on my C4 2006 1.6 auto with a similar mileage to you.
Have you had any joy yet or found a way to sort out the problem.
I had heard that changing the transmission oil / fluid might help.
April, 20, 2011 AT 4:39 PM
I am just having the solenoids and the oil and filters changed in my gearbox.
My mechanic did say that the local Citroen garage said there was a fault with the auto gearbox for the 2005 to 2007 C4 auto gearboxes. They had had a few and have either done the above (which worked most of the time) or changed the whole gearbox (which I assume was very expensive).