Have you tried restarting AE? When I have an issue like this that's the first thing i do.
Please give us more information.
Type of files you're working with and size would be helpful.
As Rob said you should give more information.. about your AE version, OS, PC specs..
i have the same problem!
I have the newest version of after effects.
I use Windows 10.
I have a Lenovo Thinkpad with 16Gb Ram, core i7 8th generation.
Hi meirav22899137zmvu & Korbinian241244638o6h,
Welcome to the community. Please share the following details.
Please try disabling Hardware Accelerated Composition, Layer, and Footage Panels in After Effects Preferences > Display.
Let us know if it brings any change.