Macbook pro 2017 scroll lag in safari/chrome

When I played slither.io recently on my Macbook Pro 2016 I noticed a lag every few seconds which makes the game basically unplayable. So I started to look into this and I became aware, that I have repeating lags in Safari/Chrome every few seconds, no matter what. It is always there. I just started to realize it then.

So no matter what, you have the lag if you type, scroll, anything. Macbook seems to pause every few seconds for half a second to a second. Unbelievable.

So I read another post in this forum from two years ago which suspected some connection with the backlight of the keyboard. But there is no difference for me if I turn it off or on or check the 5sek box or not.

Any idea how to fix it?