My puppy growls and bites when I grab him by the collar

I have a 6-month-old border collie. He’s mostly great, a bit naughty and likes to eat anything he finds but he’s already learned the “drop it’s command. My problem is that when I grab him by his collar and try to move him he goes crazy and growls and tries to bite me. It is definitely not playful and only happens in that situation; he’s okay with me grabbing his collar (the problem comes when I try to move him), picking him up, opening his mouth, etc. I don’t know what to do and I’m not sure if positive reinforcement is the solution.