What is the increasing inertia of a 10,000 kg train at rest

No increase in inertia

Explanation:

According to law of inertia we know that if a body is at rest position it will remain in rest position and if a body is moving then it will remain moving until we apply any external force

Here it is given that the train is in rest means according to law of inertia it will be in rest until we apply any external force and its inertia will be constant

As its inertia is constant so there is no increase in inertia.