I've been experiencing similar on separate computers as well as Chrome and Firefox on my phone. Using F12 and refreshing, I see following with a warning symbol...
"Use of getUserData() or setUserData() is deprecated. Use WeakMap or element.dataset instead."
Link to the right of the message points to bootstrap.js and requestNotifier.js.
Tapatalk flies.
Edit: While waiting for FF to load the site, I opened IE and logged into site. No issues. Page loads are fast.