I too struggle on this. But to stay motivated, try to look at popular ideas that you're interested in. Make it more in your own way. Make it more fun to you, so the audience would have fun as well.
Another thing is to actually go OUTSIDE. Whenever you go outside, you get ideas to talk about like what's going on or what you feel like talking about.
Think of your channel as your show. It's YOU who decide what content to upload. And people want to hear and see YOU. So make yourself more open to others and grow and actually have some fun.
I'd also highly suggest to collaborate. It could be your friend or anyone literally. Two people is always better than one.
I just typed out what came out of my mind, but yeah. Hope this helps
I'll be out for two weeks, going to beach so guess I'll take a break and find some things and topics to feel like talking about
(Any grammar or typos, I was just writing this fast on phone so yup... Sorry about that)