Interestingly, coincidentally I thought this was my problem with my Moto-Z Play restarting/rebooting… in fact, it was the aftermarket case that had either aged/hardened (soft rubber extrusions to volume/power buttons) or just shrunk/tightened and it was the physical contact with the case that was restarting the phone. Simple in the end but frustrating to trouble-shoot. Thought this might help someone else with the…not so obvious.
Bill D.C.