Sounds like your Golden needs some confidence building.
Running away and rolling over onto his back are all signs of submissiveness. It should not be punished. Don't reach for his collar when he is doing this. He is very scared. The act of reaching or looking over a dog is very dominant and will provoke a submissive dog to try and protect itself. I'd hate to say this: but his biting you is your fault. He's showing you his belly saying "Okay you win" but then you are reaching overtop of him and standing overtop of him which your body langauge is telling him "The game is not over" so then he reaches for his way to protect himself and thats to bite. If you punish this bite, you are greater risking his security and he'll probably bite again.
A few questions here:
Why do you have to grab his collar?
Has he gone to obdience training?
Does he tend to strech, yawn, shake, or lick his paws very often?
Where did you buy him?
Does he ever urinate when meeting new people?
If you can answer these, that would be great.