When I turn on the hot water tap which is manufactured by Grohe, model Italia, the water start flowing but as I turn the valve further, the tap starts to shudder and the water flow diminshes with the shuddering so very little if any hot water flows. The valve is 3 years old.

Is it sink faucet, shower faucet or tub faucet ? Also, is it "Italia" or "Thalia" ?

Sounds like a loose washer. Please answer Milo's question.