Sorry to hear about this trouble. Could you please confirm which OS and version of Illustrator is this? When did this start happening? Are there any recent changes made to your system? For example, any antivirus, system updates or web extensions installed recently.
We have recently released an update for Illustrator 2021 (v 25.0) which contains some stability fixes. If you are not already on v25.0, then we recommend you to update to latest version and let us know how it goes.