I see that there are some old topics but my problem didn’t exist for over 6 months. It just started about 2 months ago. My lights keep turning on now because the motion detector sees motion but nothing is moving. Any idea if its the motion detector or if its the hub?
I’m sure that’s very frustrating. 
What’s the brand and model of the motion sensor?
Usually the best thing to do is just to start going through the regular checklist for false positives. This time of year, it’s often the heating system, but run through the list. (This is a clickable link)
If none of those steps seem to fix it, then the next steps will depend on the brand and model.
I’ll have to look it up later.
One thing that IS weird is…I can get it to trigger if I pick up my phone and use it. WEIRD right? I can be in a different room and I can unlock my phone start to use it and boom, light turns on.
That one is weird, for sure. Are you using the phone on Wi-Fi or cellular? Which ever way, switch it to the other and see if it still triggers.
IMO those are ghost events from smartthings cloud, undesired but to be expected.