I run into this in periods due to working too much and just not having the energy. The key for me is to give up on any intellectual ambitions for a while, and just go for something that’s quick and easy to read.
After I’ve started reading regularly again, I can then ramp up the difficulty until I suddenly reach that stage again where I feel like “it’s weird how I just don’t read anymore”, and I have to start over.
I don’t really notice that I’m thirsty, so I used to go full work days without drinking anything other than a glass of water that my colleague gave me at lunch, then feeling strangely tired when going home.
The end result was a kidney stone. After that painful experience, I always have a bottle of water in my office, and make sure that I drink one bottle before lunch and another in the afternoon.
On days off from work, I still forget to drink, because I don’t have my water bottle there to remind me.