Temp Gauge Temperemental..

Hi all, Did search but only found, temp not working at all, My tamp gauge today started playing up, From cold when the engine warms up it will move to just above the minimum indicating getting warm, then it will stay there for a while and quickly go upto the middle when the engine is hot. (quickly as in shoot up in 2 seconds..)

Might rectify itself but any ideas what i can check? Thanks.

just like mine always has done