I think that's kinda weird, driving by at someone's house, watching if a girl caught the guy:p, for me that sounds dangerous too, but he might has a big crush on you, but I don't know.. You should be careful
You don't know what he's up to right? , so you should find that out.
For me it's a sign of troubles, but also it could possibly be a sign of love.
But as I said, be careful with those guys.