Question

Why current should be passed for a short time though the circuit while taking observations?

Answer 1

to complete it on time

Answer 2

This is usually a matter of power and temperature.

Resistors tend to create signal noise when heated. MOSFETS change resistance with temperature. Magnetic core materials can change drastically at different temperatures.

By letting the circuit work for a while, perhaps let it reach steady-state temperature - then see if everything works, noise, efficiency, stability