Hello gumma1030,
Does this happen with every single video you watch on YouTube?
Can you tell me what kind of connection you have to the Internet, and at which speed?
A few things you can try, if you are using Internet Explorer.
With Internet Explorer open, click on Tools at the top right(it may appear as a picture as a mechanical cog) and then click on Internet Options.
At the top right hand side click on Advanced. At the very bottom of the box click on Restore Advanced Settings, and then Reset.
Once IE has been Reset take a look in the list above for the section named "Browsing", undernearth you want to find and untick Enable Third Party Browser Extensions, Apply and then OK.
Bare in mind that streaming videos depends a lot on your Internet connections stability, loading websites and loading streaming videos are very different, gaining some information on how you connect may be helpful.
Thanks,
C.Skyco.