Your hand is bumping the touchpad slightly most likely, and in Windows 8 / 8.1 there is a setting that 'halts typing' for a set amount of seconds if the touchpad is interacted with.
To lessen the time, or stop the 'halt typing', just go to..
CHARM BAR > Settings > Change PC Settings > PC and Devices > Mouse and Touchpad > Touchpad
And set: Short Delay or No Delay
I use Short Delay. Works for me.
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