not sure try running a diagnostic, then checking what’s using up your active ram. A diagnostic to use here;
1 school ebook or personal
2 if school contact your school if not continue
3 Turn off and on, close all outside apps
4 if the ebook simply loads poorly you might have a virus or a poor model
5 if you know you have a good ebook, it might help to load everything you need onto a separate hard-drive and factory reset it, may get rid of the viruses. Hope this helps