2010 D4 Restricted Performance

My 2010 D4 TDV6 is showing an intermittent fault of water in the fuel sensor. It hasn't really affected the performance of the vehicle, but has anyone has the same symptoms? Start in the morning and she runs fine without and warning or issues. Start again second or third time and the restricted performance message comes up. Later on the message disappears again, only to pop up again later... I can't feel as difference in performance, maybe a slight lag?
Any advice? Thanks everyone...!

Have you drained the water separator/sedimentor? That would be a good place to start.

Thanks Nodge68. I'll have a look... I'll post an update once done for everyone else's benefit.