Maths, are you running under a VM?
I had to up a bit the resources of my VMs, i did also had this issue, but once i went from 1core/2threads to 2core/4threads, the stop n go went away. I also upped my VM from 1024MB ram to 1536bm RAM.
Another thing i did was to lower both "MSBetweenTicks" (to 5) and InputEventMSDelay (to 25) under Settings/Main, did also help a bit.