I've had this problem on my new MacBook Pro that occasionally when I try to use Mission Control it locks my system for 30-40 seconds before showing me Mission Control. Usually a restart will fix the problem for a period of time, whether this is a few weeks or a few minutes seems pretty random. I've tried killing the Dock process, but that never fixes the problem. I disconnected my external monitor and that didn't help.
Anyone have any ideas?
Specs: OS: Mojave 10.14.2 Processor: 2.6 GHz i7 Memory: 32GB 2400 Mhz DDR4 Graphics: Radeon Pro 560X 4096MB / Intel UHD Graphics 630 1536MB