I trapped a nerve in my shoulder whilst on holiday with the kids back in spring this year.. A kind of upwards shoving motion to splash water on them while they were at the side of the pool..
Six to eight weeks of agony and ridiculous amounts of (largely ineffective) strong opiate painkillers before it miraculously cleared up overnight..

I think I’ve just done a similar thing shoving some insulation board up into the rafters whilst helping my brother in law do some work on his house..
I can’t take that much disruption again..
Any physios able to offer advice on exercises to help free it up?

I’m not a physio but suffere from this and muscle issues after a shortening of the other shoulder after I broke it.

Google the various exercises to loosen / stretch neck and upper trapezius muscles, works for me.

My experience is that the more it goes the more susceptible it is to it, I’m afraid. It finds the weak spot. Good luck, I’ve only ever dealt with them by waiting.