In Video mode, you may have a feature called “Loop Recording” turned on. Loop Recording cuts your videos into segments to make it more managable. This is perfect when recording really long videos like when you are using the camera as a dashcam. Think of it as an auto-save feature. 

Turn this off when you do not want to have your videos in segments.

In Photo mode, you may have a feature called "Photo Lapse", also known as time lapse, where a series of photos are taken at regular interval. If you have turned this on by accident, just turn it off until you turn it back on again.