Is it normal for aging dad to obsess over small things?

My dad has no friends, no hobbies, and no family other than me and my mom. He works and then sits in his chair all the time. To each their own, but he has a tendency to be very focused on small things. For instance when he's done working, he hurries to put on his shoes and get the mail. I don't mean like he casually just gets the mail - he's so into like it's the best thing on earth. He gets the mail, looks at it, then checks he mailbox again, then looks at the mail he got out, and then checks the empty box again. Even when he's mailing something, he'll rub the stamp on the envelope for 2 minutes over and over, staring at it. He also hurries to wrap up garbage before my mom and I can even finish.
He also obsessively puts windscreen wiper fluid in our car even when I tell him it doesn't need it. He'll go out and check every single Sunday. He doesn't know anything else about a car so it's not like he's curious about potential work with it. It's literally only windscreen fluid.

I don't think it's normal to be so fixated on tiny things like this. He obviously needs something to do but idk what?