I had an experience like this not so long ago. I was walking somewhere quite late and I thought I saw a male mental health nurse with glasses & a beard smoking a cigarette (lol), so I walked to the other side of the road.. turns out there was nobody there. And when I went to cross the road, for some reason I thought this white BMW was driving and was about to run me over, so my heart jumped. Obviously there was nobody in the car, it was just parked. It was strange. A couple of little things like that happened that night, actually.
I don't what diagnosis(es) you have, but if you have one, it could be down to that if it's relevant. If not, it may be stress / anxiety related. I thought when that was happening I was developing psychosis or something, but I was very depressed at the time, borderline suicidal, and I've been told that stress and/or anxiety can manifest itself in small hallucinations/illusions.
Hope all s'well.
EDIT:
Just read the replies, well, I'm sorry I cannot be of much use then I guess ....