Engine vibrates at low RPM

Hello, I have mitsubishi lancer ex 2016 AT
6000KM. My problem is when I on D and braking
the car like in traffic jams, my car vibrates roughly,
at which the RPM is at 650. When I drive normally
and the RPM starts to rise above 700, the
vibrations goes away.
The problem is related mainly to the RPM, as in the
morning when it's cold,  I start my car then bring
the D while braking, no vibrations, and the rpm is at
900. But when the engine warms up, the rpm starts
to drop to below 700, the vibrations starts over
again.
No vibrations happen neither in N mode nor in D
mode while driving. I've checked the engine
mounts and they are all normal. I've tried some
injection cleaners and octane boosters but they
couldn't help.
Any ideas or recommendations?