Do you know why do you always start a series motor on load?

Every material has its own tolerance limit. ( you cannot tolerate your bullying friend and sometimes a boring lecture). Yes just like you the wires used in winding of series motor has a certain tolerance. When series motor is given supply it draws a lot of current to find its rotation. This may affect the wires in winding. This current increases the starting torque. Imagine what will happen if your bike picks up 110kmph when you start it. Incredible right. Same way such high torques will damage the series machine and hence it is started on load.

Simple and fun

Series Motor with load