Trying not to lose muscle while appetite goes quiet

Hi everyone, I’m very new here and on my first week. I’m 34, 5'8", around 186 lbs, and I lift three mornings a week before work. My main worry is that as my appetite gets quieter, I’ll accidentally under-eat protein and end up smaller but not stronger. I’m not trying to do a big bulk, just hold onto muscle and maybe add a tiny bit of lean mass over time. Right now I’m aiming for a palm of protein at each meal, Greek yogurt after lifting, and a slow walk on rest days. Is it too early to think about this, or should I just focus on protein and showing up for now? Sorry if this is a silly question.