This appears to be UI issue. I surmise that whenever the notification window pops up or steam's unique right click menu does, the client loads the special graphics for them. After this happens, I can immediately right click again and it doesn't freeze, but after a while of it not happening, the same issue will happen later on, possibly due to the graphics eventually getting unloaded from memory (or something like that).

This problem was never an issue for the entirety I have been using steam, but it started being an nuisance around a month ago.