Yep it happens. Some cops are like that. They just pull you over to see if you are doing anything wrongI hate when that happens.
One time going home from work it was like 35 degrees and a cop claimed I was speeding when I was going the speed limit. He claimed he had been skidding trying to catch up to me (he waited until I was like half mile past before turning to follow) and I swear it took everything to keep my mouth shut. He only gave me a warning though. Think he was hoping I'd take the bait and then give me a ticket.
Common trick question to get you to admit: "Do you know why I pulled you over?"
I always answer no. Even if I know I was speeding or something.