5mo keep looking at his hands

Yes it’s normal. It’s just part of their milestone - hand eye coordination. Don’t worry too much. Baby has lots of milestones be it major like sitting up, calling for mama or baba, or minor like hand eye coordination, etc. You may go to this website for a read (https://www.whattoexpect.com/first-year/month-by-month/) but bear in mind every bang is different - some may be faster some may be slower.