Call the experts
I would keep a journal of the occurrences, because:
1. You have a record of the inexplicable phenomena.
2. If there is a repeating pattern, this could suggest residual energy, which is often harmless.
In the case that you wish to know more, or cannot deal with the restless spirit, you could use some means of spirit communication to ask what they want, which could put them to rest, or call paranormal investigators who will use high-tech equipment to determine the source or the supernatural activity.
What to do when experiencing paranormal activity?
Keep a journal