Don't overthink it. Don't search for the perfect project. There never will be one. Just start sth, also multiple potentially multiple things, and keep active on those which are fun. It's good to do small projects (timescale: a day to a week or so) which you can maybe extend later.
Games were already mentioned, and I share this recommendation. Those are usually fun, and you have the whole spectrum of tiny to huge, simple to very advanced, touching also basically the whole stack, almost the whole field of computer science, and beyond, as much as you want it.
Otherwise, maybe some electronics? Robotics? Machine learning?
Or think about your daily routine, at work or also privately. Isn't there anything you wished would exist or improved, which would make your life easier? I have countless of small little utilities which evolved with such motivation over the time.
Games were already mentioned, and I share this recommendation. Those are usually fun, and you have the whole spectrum of tiny to huge, simple to very advanced, touching also basically the whole stack, almost the whole field of computer science, and beyond, as much as you want it.
Otherwise, maybe some electronics? Robotics? Machine learning?
Or think about your daily routine, at work or also privately. Isn't there anything you wished would exist or improved, which would make your life easier? I have countless of small little utilities which evolved with such motivation over the time.