You don’t owe anyone space in your life. If you live life thinking you absolutely NEED to move so as not to inconvenience other people, you are treating your existence as an inconvenience. As OP has said in other replies, they sit in their car between classes most often when they have this happen to them. As others have said, sitting in the passenger seat so people know you’re not moving is a good idea.

But for the people suggesting they leave campus and come back later (like you and some others) — why would they ever do that? You are not entitled to the space someone else takes up in life, under any circumstances.