I have the same problem with my Galaxy S6 Edge. However deleting the search widget didn't work. In my case it seems to be a headphone jack issue. When I plug headphones in, I have the problem. When I use Bluetooth headphones, it works fine. Of course the bluetooth phones drain the battery and the dongle swinging back and forth by my ear is a bit annoying.
Dont know if you found a solution, but I know the reason for it.
I recently ripped apart some head buds and soldered them back together in a hurry, I didn't insulate all of the wires, just the ear bud wires, the button wires were all mangled up.
So I noticed when I crunched or touched the mangled wires, which should be seperately insulated, google voice opened, music started playing, volume changed randomly etc.
So, the solution is just get new head phones, or in my case - insulate the damaged/mangled wires.