Start by inspecting the safety starter switch at the top of the clutch pedal. Make sure the switch button freely presses and releases. If not, replace it.
Be aware that bypassing the safety switch is dangerous because, if you forget to place the transmission in neutral when starting the engine, the car could lurch forward or backward and thereby cause damage or injury. However, if you still wish to bypass it, which
I strongly do NOT recommend, then short the terminals in the switch connector with a jumper wire.