I have the graphics settings in windows for the browsers to use the apu.
It was happening with other applications like steam and wowup. Changing the setting for those apps to use the apu seemed to fix it for those applications but not the browser.
After about a minute or so of getting a video to play, the issue goes away.
I can try and change the settings to have it use the dgpu and see if it continues to happen and report back.