Mms,. I never herd of such a thing at home, but they have these in public bathrooms. Yes, as soon as you get up the motion sensor flushes by itself. Aloha!
It has a slow leak in the flapper valve. Take pictures, go to a good store that can help you get a new on. Turn off water to replace. I do warn you that shut off valves get frozen! Whole nother problem!
Can you explain how your toilet flushes itself, I am sorry if this sounds like a dumb question, but I just cannot imagine how that happens to a standard house toilet.
get in a ghost buster lol
Jacx has the correct answer. The flapper needs replaced. Water leaks until it gets low enough to trigger the flush then refills and starts over.