6n hesitation

Right,

Basically, whenever the needle of my car's temperature gauge reaches the middle of the dial (it never goes past this point) the car seems reluctant to pull, sometimes hesitates when you step on the gas, and judders when you take your foot off the gas.

As soon as it cools down slightly, it's fine again. It's rare that this happens except when driving in heavy traffic, as the engine usually runs quite cool, but it's bloody annoying when it does happen.

My limited mechanical knowledge makes me think the problem is related to a sensor or something, but what? I'm really stumped.

Cheers.