In my opinion you are not seeing CPU throttling, but one of Intel's power saving features known as Dynamic Frequency Scaling or more specifically Intel SpeedStep. TheWhile idle, the CPU can dynamically reduce clock speed to reduce power consumption.
PleaseCPU throttling only occurs if certain constraints are reached, such as high temperature or power consumption. Judging from your figure neither are the case. Also it is practically not possible to tell if CPU throttling is occurring from your screenshot. Please see my question here on how to identify throttling on MacBooks: How to monitor and control thermal CPU throttling in OS X?.
In case you still think you are experiencing CPU throttling, I suggest you update your question with the output from pmset -g thermlog
as described in the accepted answer or update your screenshot with one from the latest Intel Power Gadget where the REQ
parameter gives you an indication of throttling.