Why is the Pokedex glitching

Solution 1:

Niantic released v 0.31.0 for android on 7/30/2016

Beforehand the Pokedex glitched and scrolled, just as your described. After I installed the updated, I was able to load the Pokedex and view the Pokemon with no issues at all.

Solution 2:

I had this issue and it was due to my touchscreen not registering that I had removed my finger.

A restart of the phone resolved the issue.

It might also be worth clearing your cache or re-installing the app. You won't lose anything doing this, because all of your data is stored on your account, not your phone.