The first thing to do is just put your phone away for an hour or two and see what happens. Often it's not attention deficit or fatigue, but plain old endless scrolling that hooks you way harder than we realize. Social media and app algorithms are specifically designed to switch your attention every few seconds - your brain just isn't built for that, and you end up in a kind of trance. It's not a problem with your concentration, it's how these apps are designed.
Try introducing simple limits: turn off notifications, set a timer on your phone, or use the built-in time restrictions in apps. Or just put your phone in another room during certain hours of the day - sounds obvious, but it works. After a day or two you'll feel the difference and get a clearer picture of what's actually going on with you. If you still feel sluggish and like time's disappearing even without your phone, then yeah, it's worth looking into your overall state. But ninety percent of the time, it's the phone that's to blame.