Temp Guage Issue?

[BOF crewman X8]

I started the X8 today after about 4 days, got about 50mtrs down the road and the High Engine Temp Warning came up and it started beeping, the temp guage went from C to H in about 3 seconds then just as quickly everything returned to normal. I stopped it, checked the coolant in the header tank (which was still cool as the car had only been running for about 1min by this stage.

The wife said it did it to her a few weeks ago, exactly the same thing but unless I saw it I wasnt worried, any ideas? Sticky thermostats a problem in the LS1 perhaps??

Thanks