Yes, judging by the results it's a rogue app, one using excessive RAM or CPU cycles or maybe reading/writing to memory a lot. Try and error would be best way to test, uninstall one app after another until you find the culprit. Sort apps by install date and try remember when it all started, will give you an idea where to start and which app could be causing it.
Although I can't really guess why it would slow down only the app menu.