Why my Samsung Galaxy S6 vibrates for no reason and a weird icon appears for a fraction of second?

[AC Question]

Hi everyone. Lately my Samsung Galaxy S6 started to vibrate for no reason and I noticed that in that precise instant a weird icon appears for a fraction of second on the top left of the notification bar. I used a screen capture app to make a video and managed to capture the icon I mentioned, does anyone know what icon is that and why the cell phone vibrates when it appears? Thank you very much in advance for your help, and have a nice day

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