Notebook interface is freezing

the notebook interface freezes for a second or two whatever I do, like copy-pasting , just switching cells, scrolling page or other usual browser interface operations. This is being observed both in chrome and safari browsers.

Also, notebook is jerking while starting and loading fonts or "proccessing math". Can not see any errors in the terminal.

Other programs and browser tabs work perfectly well, as the hardware is quite powerful.

I have got some nbextantions enabled, wonder if it causing the problem.

Start by reproducing the freeze and startup jerking in Jupyter Notebook using Chrome and Safari, checking whether enabled nbextensions affect the behavior. The issue is done when the cause is isolated and the notebook no longer freezes during copying, cell switching, scrolling, font loading, or math processing.

Written by the indexing model from the issue text.