Leave your performance monitor running while the hangs occur. I'll bet you see some spikes in usage from some driver or a specific process. Also of course check your event viewer. Perhaps these are some "silent crashes" of something in the background that drag the system down.
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.
It's an intermittent problem, so it's been frustrating to troubleshoot. I actually got on the Adobe chat the other day and shared my screen with the service rep. He deleted the Media Cache folders and then cleared the cache in AE. Since then it seems better, but I'm still getting more crashing/not-responding problems than I had with 2016 (which was pretty darn stable!).
I've tried keeping tabs on the system activity, but as I'm usually working hard with deep concentration when this happens, it's not been easy to spot things. When I get the "not responding" problem, it doesn't seem that the CPU or RAM or Discs are maxing out.
I don't know how to use the "event viewer" that Mylenium suggested...I can start it, but don't know where to begin to look.
I'll get back in here if I find anything useful or definitive. Thanks for your help!
You may want to get back in touch with support and let them know the fix didn't work. Let us know what happens.