I'd definitely agree with going bigger rather than smaller. I've got some hand shakiness myself from years on the road, and when I picked up model building as something to do during winter breaks between hauls, I found that 1:24 scale is genuinely easier to work with than the smaller stuff. The parts are substantial enough that you can actually grip them without feeling like you're gonna crush something, and the instructions are printed larger so you're not squinting constantly. 1:64 might look like an easier entry point, but honestly those tiny pieces are a nightmare when your hands aren't rock steady - I've watched my nephew with perfectly still hands lose patience with them.
A proper desk setup will help you way more than chasing a smaller scale. Get yourself a decent magnifying lamp with a stand so your hands are free to work, and maybe a hobby mat with some grip pads to keep pieces from sliding around. I use a simple desk clamp light with a 3x magnifier and it made a massive difference. You don't need to spend a fortune - I've seen decent setups for under $100. The magnification and good lighting actually make your tremors less noticeable because you're not fighting to see what you're doing.
Start with a straightforward Tamiya 1:24 kit, something without a ton of tiny detail parts. The plastic cement and paint will take some practice, but that's where the magnifier and patience come in. Take your time, do small sections, maybe work for 20-30 minutes at a stretch instead of marathoning it. The actual building becomes meditative once you get into a rhythm, and honestly it's kept me saner than anything else I've found during those long winter stretches when I'm not hauling.