What OS, how old is the laptop, what CPU, and what security program runs resident?
Many possible reasons, including (a common culprit) too many programs running at system startup (Click "start>run and type msconfig, push enter, select "startup" tab. How many entries are there?)
One application that can "free" memory is a tool in Advanced Windows Care, by Iobit. I doubt it will fix the pausing issue, though.
Does this only happen when streaming videos, or any random time? If the latter, open taskmanager and next time it happens, see which application is using high CPU.