Thanks for the advice lads.
No idea what’s caused it really as I’ve never done physical work and never played much cricket once I’d started work.
My son read up on it and it seems running can be a cause because of the constant pumping action of the arms.
I’ve noticed that in general,as I’m closing in on 59 I’m getting more muscle stiffness and spasms.
I’m aware of MS and Motor Neurone as I’ve had three people who I know who’ve died from MNE in the last decade,I know the symptoms and I’m not suffering any of the other markers.
I know Polymyalgia and Fibromyalgia can cause this sort of thing.
It’s the randomness of the pain though,all is fine for hours and then one wrong move at too higher speed and it feels like you’ve been knifed!