Hi, when accelerating smartish from junction there feels like a 'jolt' and 'gearbox fault' displayed on dash. The car continues to drive but slower (limp mode?) . I pull into a car park and turn ignition off, wait a few seconds and restart no problem and drives normal. This is second time, first about a month ago.
Appreciate any ideas?

 

Forgot: 58 plate, X-Type 2.2 Diesel.

 

I lived in the UK once, hence I know that your information "58 plate" is supposed to give us your model year...
The thing is: No one outside of the UK understands that code. Thus: Which model year?

Fun fact: I just saw a really cool plate here in NSW/Australia: "66PONY". That guy pays a lot of money every year to keep those plates - and it is obvious, what car it is on: A '66 Mustang - a beautiful red one.

What's the mileage?
Did you ever do an ATF change (Automatic transmission fluid)?
If though: Which ATF did you use?