Can I ask my father to stop stalking me?

So....as someone who's been a tenant my entire adult life, yes, a landlord has to give a notice period before coming in, but no, they don't usually have to give one before coming on the property or driving by their property (the laws might be different where you are). You might consider changing the locks. And - not that you intend to do anything legally about his drive-bys, because he's your dad! - but I just don't think there would be anything a normal tenant could do about it, except maybe keeping the curtains closed and parking away from the property. (A drive-by stalker would have to have threatened a person in order for the police to do anything at all....and even then, a person may or may not get a restraining order, but no arrests unless the order was breached.  Judges give these out to prevent violence, not nuisances.)

That said, I do feel your pain. I started staying with my mom in order to provide care, and in the beginning, I really hated having to tell her where I'm going or where I've been! I haven't even lived in the same town with her since I was 15, so....

My mom doesn't respond very well to the answer, "Out." But I did it anyway, because I'm 49 and I refuse to be accountable for my whereabouts.

If your dad isn't responding to gentleness, I think it's okay to say, "We've had this discussion several times, dad, and you know it's my own private business what I'm up to." And be a broken record about it.

If you’ve had no relationship with your father since you were 17, he may simply want to get to know you. However, this familiarity obviously makes you uncomfortable. Have you considered hiring a company like 1-800-gotjunk to speed along the process? You can also answer a question with a question. “Why are you home?”...”Why do you need to know?”...

These are all good answers and I've tried being gentle. We had a discussion about privacy before I moved in. I regularly have to remind him I'm a "grown up"! If someone else was renting the house he'd by law have to give 48 hour's notice, he couldn't just use his key to come in anytime and if they saw him driving past, could have him arrested. I invite him over 2x a week, one of which is the entire day Sunday - one of my 2 days off. Thanks again though for suggestions.

While I agree with polarbear and smeshque about what is likely, I don't rule out the possibility that he would like some control over you, his child.

Be pleasant. Answer his inquiries if you happen to feel like it, or give a silly response. If things escalate and gentle responses aren't working, you can resort to "Dad, you seem to forget I'm 57 years old and can make decisions without your input."

But start with, "I'm home today because it is my day off and I'm using it to work on clearing the guest bedroom."
"Well Dad, I didn't get fired if that is what you are worried about! I'll have enough money to pay you this month's rent."
"Next time you are in the neighborhood and notice that I'm home, stop in and I'll show you the progress I have made. If I have time we can go out for ice cream."

Assume that he is not stalking you. Only ask him to stop if more gentle measures don't work.

I agree with polarbear, he probably just misses his home and life.
I don't suspect his intent is to stalk you.

I suspect your father misses his old home where he had lived for 30 years. I doubt he wants to stalk you. It's more likely that he wants to visit his home where he made a life and a lot of memories.