Sometimes, when I engage "D" from "P", I hear a loud "clunk". This usually happens when I leave the car parked for some time. Is this normal?
There are a few possibilities here.
Firstly, if while parking the car, the lever was shifted to "P" while on a slight incline, the car might roll a few centimetres before the parking lock takes effect. This is because there is a slight free play in the parking-lock mechanism.
Under these conditions, there is likely to be a "clunk" when you shift the lever out of "P" as the lock is released. This is not abnormal and nothing to be concerned about.
Another common cause of the noise is higher than normal engine speed - which is bound to occur whenever you start up a cold engine. This too is not abnormal, but if you feel that the noise has worsened noticeably over time, you should have the transmission checked.
Usually, flushing and renewing the transmission fluid with the manufacturer's recommended type and grade will alleviate cold-start shift shock.
At the same time, check that the engine and transmission mountings are in good condition.
A broken mounting can cause varying degrees of shift shock, which will be particularly severe while shifting from "P" to "D" on high idling speed.