Hello Leanne,
Thanks again for your answer.
I do not have any other add-in turned on. And yes, I definitely have many big images (art history thesis), but I have checked if this could be the issue by copying my file, deleting the pictures and adding/editing citations, and the lag is still there. I also deleted any sort of tracked changes but Word still goes unresponsive for several seconds.
I have also tried splitting the document in half and I have also checked the document for inconsistent citations by unformatting and reformatting everything once again, and all was fine…but the the lag persists…