Can I be pulled over for that?

I live in a small, suburban community in Minnesota. Any time I venture outside after about 11pm I can be pretty sure of getting stopped by the local police, especially if walking or on a bike. Generally, the questions consist of, "How old are you? Let me see your ID." which is then followed by them checking my background for warrants, etc. I can understand this action when on foot, because in my community, walking at night could almost be considered suspicious activity, but what concerns me is when I get pulled over in my vehicle... I was under the impression that there are certain rules and conditions that police must follow in order to have a legal reason to pull over someone's vehicle, but lately I've been pulled over for such reasons as, "I saw you driving around at this time last night and just wanted to see what you're up to." (I was driving at 1:30 AM, about 20 minutes after the time I get home from work.) He proceeded to check my record and let me go. I mentioned that it was the time I get home from work and he'll probably see a lot of me. I'm just wondering if this the type of behavior is something I should just come to expect from police, or have they been overstepping their bounds a bit?

I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.

This would probably be called overstepping. If police stop you for no reason, then that is under false pretenses.

If they stop you for a traffic violation, that is one thing. If they stop you for stalking around one neighborhood, that is one thing. But being stopped because you are out late at night, coming home from work or a party or whatever, is something completely different.

Is it the same officer? Do you feel safe to report this person/persons?