In short, make sure that your source footage properties matches the properties of the timeline and make sure that the export settings match those properties as well. For example, if you have 1080p25 footage, edit in a 1080p25 timeline and export as 1080p25. If you deviate from that all sorts of issues start to creep up, stuttery playback of the exported video is one of them.
Those problems can happen in other situations as well, so post screen dumps of the Sequence Settings and the Export Settings dialog with the Summary as per the attached image below. And last, what are the properties of the footage, 720p25, 720p50, 1080i 25fps, 1080i 29,97 fps or what? To attach images, use the button in the screen dump below.