A few things to consider...
Try side projects. Could be something you're been thinking of trying out (scratching an itch), or to learn something new.
For example, recently I made a macOS Quicklook plugin for displaying the Basic listing for program files for the first 8-bit computer I learned to code on (https://github.com/sebastienboisvert/ZX81QuickLook).
Another one I'm working on is modernizing support for a USB video capture device (https://github.com/btrask/EasyCapViewer).
The first one was a lot of fun for me, as it got me back to my 'roots' (re-acquainting myself with Z80 assembly, besides the nostalgia aspects), and along the way I learned some of the newer features of CSS and JavaScript (it had been so long since I worked in JS that I didn't know it had async functions now!). The second one is out of my 'comfort zone', and is forcing me to learn some new unfamiliar frameworks that need to replace the old code.
Initially, I wanted to only allow myself to start on them once I had completed doing a lot of other things that needed to get done (being such a procrastinator) - but I found that just doing them without those restrictions relaxed me more, and allowed me to get those things done more easily anyways (it served as a diversion, but a good one that I didn't need to feel guilty about).
If you're coding day-in day-out, doing the same routine, think about 'tuning out' at night - leave the computer off, and do something else altogether; take up a new hobby, or read some books, or anything that interests you. The point is to change the scenery a bit to recharge.
If it's available to you, you might consider taking on (or asking for/seeking) something that's new to you at work, that opens up new opportunities, both for learning and potential advancement. Any good employer should recognize and appreciate that.
As others have noted, 20 years is fairly long time, especially if you've only done the same general thing; as such, it might also be worth considering a bigger change. Maybe it's time to take on something else that's more challenging, that can help you grow. That could be something along the tracks of a more managerial nature (or simply taking on more of a leadership role, if that sound too scary), or perhaps something in an entirely new direction.
There's a lot of good feedback here - soak it in, think about it, and consider what might help you get that excitement back. Making changes doesn't mean you give up what you love doing - it might be simply the thing you need to rekindle your interest in it.