Hi LittleClaire, I'm in a similar situation, with shoulder length naturally wavy hair that to my great surprise started to become more curly than wavy in mid-late 50s

& now bears little resemblance to how it was throughout my adult life prior to this

. Straighteners don't work well for me so I try to work with the wave/curl instead, using round brushes to style (I use that term loosely

) as I blow dry it. Now in my early 60s, dark blonde turning white, it's gone from very thick to much finer & has become increasingly unmanageable with a kind of coarse, floaty top layer

that's very dry & impossible to style. At the slightest hint of damp it frizzes terribly!
I've washed & blow dried my hair every day since teens, necessarily, as it looks like a badly constructed bird's nest after a hurricane when I get up in the morning & is definitely not presentable otherwise.
I used Aveda "Dry Remedy" range with good results for some years until, in my mid-50s, they changed the formula & it no longer worked for me.
In my bathroom cabinet at the mo are the following:-
OGX biotin & collagen shampoo & conditioner
OGX rescue fusions hyaluronic acid & Vit B5 hydrating shampoo & conditioner
Aveeno smoothing (the blue flash bottle) shampoo & conditioner with rosewater & chamomile
Dr Organic (Holland & Barrett) Vit E hydrate & restore shampoo & conditioner (good for days when the scalp feels irritated, but hair defo needs the conditioner used with it).
I tend to rotate what I use & some days each of these shampoo-conditioner combos works reasonably well for me, some days, inexplicably - not! The unpredictability is a nuisance on days when I really want to look my best. They may not work for you, but if you haven't tried them, might just be worth the experiment, especially if you can get them on offer - the only way I buy any of them.
For blow drying I use either Schwarzkopf moisture kick spray conditioner or a little Toni & Guy leave in conditioner (cream). I sometimes mix the cream with a tiny blob of L'Oreal Elvive extraordinary oil. These are all light when used sparingly & don't leave discernible residue.
I wish I could say these all work brilliantly for me, but the truth is they are the best I can currently find, having binned countless other products over the 20 year course of my horrible peri & postmenopause history to date.
I hope one or other of them might work for you & that someone else comes along with some miracle recommendations for us both

.
W x