A month ago my temp gauge started reading 1/4 when the ignition was switched on (no engine started yet). The car was difficult to start but started eventually. After this it ran fine. After it had done this a couple of times the 'engine emission' light came on (little orange engine). I had the car tested and a new lambda sensor put in. This was after the same sensor was replaced under warranty two years ago. The car ran fine for a while but twice it did the temp gauge/difficult starting.
Just 2 days ago the car went in for a service and MOT. It passed easily and nothing flagged up under diagnostics. The coolant was flushed and changed. The next day I was driving at 70 on the motorway and I noticed the temp gauge 2 notches below the red. I stopped to check everything was ok. I continued with the gauge reading hot but occasionally dipping to the 3/4 mark then jumping up again. When I reached heavy traffic and was stopped idling the gauge returned to normal!. When I started moving freely it jumped to hot again. On the return journey it read hot again, but only on the motorway - not in the city. I checked to see if speed affected it - 50, 60, 70 but it behaved the same. The fan was blowing when I stopped and I checked the engine. It was cool enough to touch and all the time the car ran fine. I checked the mpg figures on the journey and they were normal. This morning I turned the ignition on and the temp gauge jumped to 1/4 as per the picture. The car just did not want to start. It did eventually but it took a while. Any ideas?