I don’t remember how I did it on my Samsung Galaxy S8, but I was able to get the vibrations down from the four that OP is mentioning (two vibrations, pause, two vibrations) down to just one single vibration. I believe it was something within my phone’s settings panel.
However, two days ago I ran a software update on my phone, and now I am back to the original four vibrations pattern… I was hoping someone else had found the solution to this issue because the four vibrations are pretty obnoxious throughout the day.