One thing or another limits (controls) the flow form the nozzle. in ideal operating conditions, the molten/softened plastic is kept in a small pool in the nozzle, without high pressure, and responsive to pressure by flowing from the nozzle. The plastic must be viscous and self-adhering enough that gravity and residual pressure on the melt will not be sufficient to draw the plastic out.
If the plastic is too stiff, such as through not being at a high enough temperature, as the filament is fed by the extruder the pressure will increase until the pressure is high enough to force plastic from the nozzzle. The plastic that is being fed by the extruder elastically compresses to generate the pressure. Hooke's law in action. This causes a delay at the beginning of extrusion, and a continuation of extrusion at the end. The elastic "wind up" of the filament gives us the delay. A printer in this mode will appear to work pretty well. It may require higher "retraction" lengths to unload the pressure.
If this is the operating mode, the filament outflow rate may be less than the rate at which filament is passing through the extruder. Pressure continuallly increases until the extruder motor has insufficient torque, at which point it skips. The pressure is not reduced very much by the skip, and plastic continues to flow, lowering the pressure until the extruder can again advance the filament.
It might be worth increasing the temperature.