There's a Cat in My Car

So today was a long day. You know the type. Just wanted to get home, maybe order a pizza, and not think about anything. I walk out to the car, it's freezing cold outside, and I open the driver's side door and there's a cat. Just sitting there. In my car. On the passenger seat like it was waiting for me to start carpooling.

It didn't even run. It just looked at me with this sort of bored expression. Like I was interrupting its nap. I'm pretty sure I've seen this cat around my apartment complex before, just wandering around, but I've never been this close to it. It's a kind of sandy, grayish color and honestly it looks a little grumpy. I stood there for a full minute with the door open, just staring at it, and it just stared back.

My first thought was to shoo it out, but it's really cold tonight. Like, freezing. And the cat seemed pretty settled in. I just couldn't bring myself to kick it out into the parking lot. What if it was sick or lost? It didnt have a collar on, at least not one I could see. So I did the only logical thing I could think of at the time which was probably not logical at all.

I got in, closed the door, and drove home. With the cat. It just sat there the whole ride, perfectly calm, looking out the window. So now I'm home. And there's a cat in my garage because I let it out of the car in there so it wouldn't just bolt into the street. I have no idea what to do next. I don't own a cat. I don't have cat food. I just have a random cat in my garage. What is the protocol for this??