puppy behavior problem

Question
I have a pit bull/bull mastoff mix that is 11 weeks old.  He is a great puppy with the normal puppy chewing, nipping at our feet etc.  In the last couple of weeks he has had complete freak outs, meaning if I try to touch him or calm him down by petting him or holding him, he tries to bite me and is very agressive.  Then a few minutes later he's fine.  I don't know if he is getting overwelmed or what.  Any advice?  Is there something wrong with him in your opinion?  I am planning on having him trained but I'm not sure how old he needs to be for that.  Thanks for you help.

Answer
Do you know where this pup came from? If it was a petstore, that may explain the behavior, I think though, that you should look into hiring a trainer immediately. They can start as early as 8 weeks with puppy stuff and this needs to be addressed. It may not be anything at all, but we need to be sure.
thanks and good luck
nancy