I don't think minimising the OP,s concerns is doing anything to help or support her.
It's a tired cliche that men have affairs with much younger women at work. Plenty of women post on here having discovered that very thing so, whilst it might not be the correct assumption in every case, it's certainly not a silly concern.
And, yes, for whatever reason, many young women are flattered by the attentions of an older man 🤷🏻♀️
Also, women posting on here speaking from their own perspective isn't helpful. I'm 48. I work with a very attractive 29 year old man - good looking, dresses well, goes to the gym... I'm old enough to be his mum. I recognise the above but have absolutely no interest in him whatsoever - he's only a few years older than my son and, even if I did fancy him a bit, I'd have enough self awareness to know that he wouldn't be interested in a woman old enough to he his mum when he could probably have his pick of women his own age. Unfortunately, men don't think like that in the main.
OP, you say he is taking more care of his appearance in general. In what way? Is there anything else that concerns you?