What is your internet speed? Who is your ISP?
Have you tried power cycling your router?
As a test, can you briefly try Now on your mobile phone, with its WiFi switched off, to see if that buffers also?
And say what speed you get there? Ookla is good for that, or fast.com on a browser.
What browser are you using?
What speeds do you get on www.fast.com ?
I would recommended deleting all cache, cookies and browser history - as that can slow down your browser performance but checking your speed first, is the key.