If you open 'logs' and keep it running for a while, are you noticing any devices that might be spamming your hub and causing it to both work really hard constantly and perhaps making it memory consumption not fun?
I had this happen to me and the culprit was a z-wave multi-sensor that was pinging me constantly. Luckily using a customer driver i was able to instruct the device to only self-report every 5 minutes instead which is all I need and honestly probably too frequent as it does report whenever there is a change or activity automatically.
Another common question is if a safe-reboot of your hub fixes your issue, there are some good threads [1] [2] about that including some work-around people have created if they can't get to the crux of what is causing the issue (which I'd highly recommend you do v.s. working around the issue).
