Welcome to the forum! This is a very important question, and one that I think many of us are struggling with or have been at some point. I really appreciate you taking action on this and asking about resources publicly. 

Probably my favorite write-ups on this topic is Replacing Guilt by Nate Soares. The first part addresses "listless-guilt" - that feeling that there is something that you should do but you don't know what and there is no specific motivation to guide you. 

Here is a relevant question that has been asked on the forum previously, and may have further sources. 

I also want to remind you that it's perfectly okay not to feel motivated right now. This can come in waves, and you might just randomly come across something which would make you motivated again. It's tough to feel motivated without supporting community and structure (if that's the case you're in). You might also consider joining the EA Virtual Group, or volunteer for an ongoing EA project.

You might want to read some essays from Effective Altruism Handbook: Motivation Series. I especially like 500 Million, But Not A Single One More, it is short and powerful.

One thing that probably helps me stay motivated is listening to the 80000 hours and the future of life podcasts. It's lower effort (for me) than e.g. reading essays and hence a good option for periods where I'm especially busy. I don't know how motivated I'd feel without them, but I suppose hearing from lots of people who try to improve the world can be uplifting and maybe even more personal than blogposts. This might not work if you're not a 'podcast person' though.

Enough meditation seems to pretty reliably increase empathy. My guess is there are studies purporting to show this, but I'm making this suggestion mostly based on personal observation. There's some risk of survivorship bias in this, though, so I don't know how repeatable this suggestion is for the average person.