Let's first start with a definition:
What is Deja Vu?

This expression comes from the French and literally
translates as "Already Seen"

So, in a simplistic way, yes... Everyone may find
himself/herself in a situation where you have seen
something before. The common use of this expression
however also implies that You can't remember much
about that at all and is usually followed by an
unsettling feeling...

What could cause this?
we currently understand very little about the human
brain, what it unconsciously registers when and where
Could the brain, at this moment it happens, be replaying
in the background a similar situation that it has
previously encountered/registered and about which we
have no recollection?

Just think of this... The same way, we inherit our
ancestor's genes and therefore emulate their physical
traits!? Could it be that certain fragments of memory
genes transmigrate to the descendants? This is why
(probably) one finds certain people whop are able
to know the details of a specific chunk of history
details that are not documented anywhere and are
later verified to a high degree of accuracy by
investigators... The details sometimes include the
exact location of a piece of property in a certain
area or an historic event that actually took place
and may even contradict knowledge of the current
known facts

The magnificent brain we have been blessed with and of
we know not much may decide to replay a situation
at any time based on certain triggering factors

could we have seen/done something in a dream that we
recollected and that's popping up now?

One could go on... (but time...)