I hope your problem soon goes away. It's not uncommon. I've read aboutit on other sites and they mainly suggest it's a subconcious axiety causing the grip to tighten. The answer is to relax and loosen the grip.
I'm not saying that's the case but if you are concerned each time you go out it could be self prophesising. Is it worth just going round the block for say 5 mins and if all ok do it again? That way you could build up to longer times and see if it helps.
G'Day and welcome from one of the Aussies. My left hand does pretty much the same, at least i can move it and get cirulation back into it without letting the trottle go.
You'll have to find a solution to your problem, your living near the best riding in the world! I've had that same issue come and go over the years, but with the ISO grips it's never happened since. I had my grips installed by Kuryakyn during the rally and I'll never go back.