Help with previewing movies on my iphone 8gb

[Caitsmama]

Hi, hoping someone can help me.. I am trying to preview some movies on my iphone 8GB and as i preview them, it keeps pausing on me and i have to keep pressing play... i don't want to buy a movie or rent one til' i can figure out why it's doing this.. I was hoping to rent a couple movies for the plane when we go to WDW in a couple weeks...