Is Money received from the sale of a second-hand car included/excluded in National Income?

No,

It will not be included in the national income because receipt from the sale of second-hand car is by virtue of transfer of an already existing object and it does not contribute to the current flow of goods in the economy.

The money received from the sale of a second-hand car leads to the double counting as it value is already included at its first sale.

Thus the sale of second-hand assets is included in the National Income.