Typically - a compressor stall/surge will result from the VIGV/VSV being too far OPEN for existing compressor parameters (T2 and Nh). This could result from (e.g.) a brief recirculation event - exhaust gas reingestion - which is too quick for the CIT sensor to instantly respond. Thus the stall/Nh rollback/torque drop.
(You didn't specify whether this was a fixed wing or a helo; I think this scenario could apply to either when taking off in a tailwind)
But after a second, the CIT sensor "catches up" with actual inlet temp, the VSVs close to the required position, the stall clears, and things return to normal. Note that the variable vanes are not closing to CHANGE (increase or reduce) airflow, but rather to maintain near-optimum AOA on compressor airfoils.