It sounds like a plugin acting up to me. I’ve had that before. You could try and find the culprit throught the process of elimination by disabling plugins via the ‘plugin manager’ (which you can access without opening a project).
Or you could go the other way around and create a new project and:
Add a (suspicious if you can think of any) plugin → save project → close and re-open project → add another plugin → rinse and repeat until you find the bugger.
Worth a shot. Good luck! 