audi_519

hi, just had a question about my 00 audi tt quattro 180t. I noticed for passed few mornings that when i start the engine my RPM is staying really low (200-250). before when i used to start it, it used to go to 1500 than slowly as the engine warmed up come down to 650 to 700. and the funny thing is when i start it after work which the weather gets a lil warmer ( i live in ontario mornings 2c and afternoons 20c) the problem seems to be gone and everything is back to normal. this problem just started for past few days and i have no idea where i can start to look. thanks for any input.