hi guys . my car have strange problem . at cold start there's sound like whining and clunking . after its fully warmed up it come and goes while driving the sound's become like grinding

I went to mechanic he said transmission and driveshaft mount's rubbers bushing after he checked there's nothing bad then he said it's the engine mount !
​engine doesn't vibrate that much just normal vibration at cold start

the noise cannot be heard from outside the car or under the hood only from inside I would say it comes from back of the engine to the middle of the transmission at that area

my thoughts is the torque converter or low fluid or hidden problem in the from suspension system .

appreciate any help .

thanks.