Google just recently released the Android Security Bulletin for January 2018. Unfortunately, some Pixel and Pixel 2 users have reported experiencing laggy performance after sideloading the update. These users report a general slowing of animations in the phone, and long waits for apps to launch. There is an easy fix, which is a good thing.
Pixel and Pixel 2 phones are usually first to receive Google’s Android Security Bulletins, and it was the same for the recent January 2018 patch that rolled out. Users experienced a long wait to reboot after the sideloading the update – that is, downloading the update image from the official download page and applying the update manually. After the reboot, Pixel and Pixel 2 phones were laggy.
Google has acknowledged this issue, and it said that the issue only appears when you sideload the update. Users who waited for the OTA update did not experience the issue. The solution to this issue is fairly simple – it can be resolved with just another reboot. After your reboot, the phone should now perform normally.
So if you’re experiencing this issue, another reboot should fix it. This is also not to say that sideloading an update is not recommended – there was just an issue with this particular update.