It could be a number of different things. Micro sd cards are rated in different classes depending on quality. Class 2 being the lowest, and I believe class 10 is the highest, don't quote me on that though. Class 2 cards could cause complications with the footage. From experience I have found class 4 and up works fine.
There are also different video settings that affect frame rate. I would recommend the 720p 60fps setting. This allows for smoother slow-mos, and is just better for action in general.
Brandob9 could be right as well. Computer specs can affect how the footage runs.
If you are trying to play the footage directly from the micro sd card, this will cause it to be choppy. Its important to import the footage onto your computer, then play it.