2 year old struggling with self initiation

Our nearly 3 year old son has been potty trained for over a year. He does great telling us when he needs to poop, but with pee he usually pees a little in his pants, then stops, and we’ll notice and say “oh, looks like you need to go potty” and then he’ll go. He changes his pants on his own and is otherwise fully independent with the process.

We’ve tried rewards for staying dry all day, as well as consequences like taking away his Tonie box for a short time. We’ve tried encouraging him to listen to his body. “Does your tummy feel full? Hmm you’re dancing around and grabbing yourself, that usually means you need to go potty. Let’s go really quick then you can go back to playing.”

We have potty breaks built into our routine. Upon waking and then about every 2-3 hrs during the day and before leaving the house and before nap/ bed. He can hold it for that long but as soon as we go longer or don’t prompt him, he dribbles again.

He’s starting morning preschool in September and I am concerned this will be an issue. His older brother did the same thing for a few months but eventually stopped.

Please help!