Being able to sit unentertained for twenty minutes is a skill. Most people lost it around their first phone.

Sitting with nothing arriving is a capacity rather than a virtue, and like most capacities it fades without use. There is always something available now, so the situation where you simply wait almost never occurs, and the tolerance for it quietly declines. Nothing is wrong with you for finding it uncomfortable at first.

Practise it in small amounts. A queue left unfilled, a bus ride with the phone in your pocket, ten minutes in a waiting room. Start shorter than feels worthwhile, and notice how quickly twenty minutes stops feeling long.