Grinding Noise During Start

MINE IS A 89 300SE.
I HEAR A GRINDING NOISE FROM UNDER THE CAR, MAYBE FROM THE ENGINE/TRANSMISSION AREA DURING THE TAKEOFF ONLY. OTHERWISE THE CAR RUN GOOD.
ESPECIALLY WHEN I TURN THE WHEEL OR WHEN THERE IS SOME LOAD/PRESSURE LIKE ON A HILL.
WHAT CAN IT BE?
wHERE SHOULD I BEGIN TO LOOK?

WILL APPRECIATE ANY OPINION!