My sequence starts smooth then gets "jumpy"

I'm using Premiere Pro CC. I have my clips in my sequence. The problem I'm having is when I play my sequence it starts out smooth and looks good, but after a minute or two the video starts to get "jumpy" like all of the sudden its jumping from frame to frame, or like stop motion. I'm not able to select CUDA drivers for CC. What else can I do to fix this?

JC