How is your touchpad setup? Depending on its settings it could be getting confused when you palm brushes it during typing, it pauses keyboard entry while it waits for your to to see what you are doing with the cursor. Probably set with synclient but I have not used Manjaro since it was brand new so I don't know. Lockeddrag/timeout, palmdetect, singletaptimeout and probably a few other settings could cause this, simple test is just to disable the touchpad and see if it keeps happening. If you only notice it while typing this is a good bet.

Edit: No, singletaptimeout could not cause this, was not thinking straight.