I had a similiar issue (IMO due to the short and diverting nature of social media).

I decided to read a little bit every evening. In the beginning I skipped a lot of evenings, did a lot of book hopping and, never finished a book either. I also struggled with reading a longer time at a stretch or even whole chapters. But eventually I got better.

In my case I had to learn again to immerse myself in something that doesn't reward me after five seconds, but after 15 minutes or longer.