In Firefox 70, there is a new feature called kinetic scrolling [1]. If you scroll the web page using trackpad (or possibly touchscreen), the scroll event will not stop immediately after releasing your fingers, but it will gradually slow down, as if a rotating wheel slowly stops. After using it for a short while, I started to hate it really quickly. The problem is that the slowdown-and-stop occurs very slowly and if you just want to scroll the webpage to continue reading, you need to wait several seconds until the page fully stops moving. That’s really annoying. Fortunately, this cool new feature can be disabled. Just open about:config page in a new tab, search for apz.gtk.kinetic_scroll.enabled and set it to false. Tada! No more kinetic scrolling.
[1] I found these related Mozilla tickets: #1213601, #1564238
Kparal's Fedora Blog 
I’ve been sporadically searching for ways to resolve this for over a month, I had no idea “kinetic” was the keyword I was missing 😀
I tried searching for smooth scroll, autoscroll, scroll not stopping etc but just found a bunch of other scroll settings, I’ve been tweaking the various scroll durations to no avail
This is the trick that finally got my scroll back to normal, much appreciated!
Happy to help 🙂
Thank you!
Awesome! No idea this was what the “feature” was called but I also hate it. So glad I found this page Thank you 🙂
Thank you for this. It boggles my mind that they add something like with without giving an obvious way to turn if off. It’s also in fricking Thunderbird now, where you have to locate the “config editor” to find these same kind of hidden settings.
Took me a while to find this but it is exactly what I was looking for. Thank you!
This scrolling behavior had been bothering me for so long. Thank you for posting this!