I found with the newly potty trained that it was common for them to pee after lunch but then have to go about 20 minutes later. Same thing with the 20 mintues after drinking at snack and it used to annoy me cause we would have snack then go down to the basement playroom and seemed like we just got started and they had to go pee - which was upstairs so lots of stair running.
Once I changed the schedule to eat lunch earlier and then have everyone pee that was potty trained and then sit down to do stories, some kind of group quiet activity and then do diaper changes and put babies into bed while older kids took off shoes and put them on the shelf. Then go pee again for the older kids and most of them would actually pee both times or those that just tried the first time would pee the second time. Solved the waking to pee issue. Your child may jut need to have the chance to go twice after lunch before laying down.