My car is trying to over heat after i've driven it for about 10 mins or so. Its not over heating now because its cold where i'm staying and i try to keep the heat on for my kid. But if I turn the heat off then it will rise above the mid mark and I would have to cut the heat back on.

Can anybody tell me why its doing this?

Thermostat is giving out, sticking closed.

What he said.