2002 Citroen C5 Automat gear malfunction

Hi

My Citroen C5 is sometimes giving faultmessage 'Automat gear box fault' and automat gear and triptronic is out of function, and sercice light goes on.
This happens in the first 5 - 10 mins after start and engine is 'cold', typically when going to work each morning. To get automatic gear back to normal I just stop engine and start again.
The fault seems to occur when scitching up from 2nd to 3rd or down from 4th to 3rd gear. If I use manual switching (triptronig) I normally avoid this fault.
And also when engine is getting warm, all OK.
Another issue is that the engine judder at 2000RPM in 4th gear.