Why wont certain websites load until I restart my Mac? Same happens when uploading a picture

This happens about 2-4 times a week and it is very annoying. I have a new MacBook Air laptop and with certain websites it won't load until I restart my computer, then the website loads just fine. It happens on only 1 or 2 websites that I frequent. Also, when uploading a thumbnail picture on my YouTube video, I'll click on the "upload" button and nothing happens. The folder doesn't pop up. I'll restart my computer, and finally the button works, the folder will pop open.

Why is it doing this?