The reason mentioned above is applicable to situation where you observe fluctuation in rankings within a span of 6-12 hours.
However your email states that you observe this behaviour within a span of 1-2 minutes. It could be possible that your BROWSER CACHE is conflicting with actual rankings shown by Google.
If you observe any fluctuation again, then try to use a seperate browser, and then see if your fluctuation is still showing. Or else, you should try to clear cache, history and cookies within your browser settings
I am sure it will help you resolve this issue
