my 4 yr old comes out with completely random and unrelated answers to questions quite alot. i think he is just being a typical child buy my partner thinks there is something wrong with him. sometime i read him something and ask him questions but get totally unrelated answers back.
is this normal behaviour as i am now starting to worry about it?
I would definitely not worry about this - I'm sure your first impression is the right one, in fact I think this is one mannerism that makes children so wonderful to listen to!
My daughter (now 10) used to come out with bizarre questions and answers, descriptions, comments etc and I listened in amazement and awe, trying to figure out how she made the connections in her mind. She's now 10 and much more "logical" but less fascinating! As long as your child can make some logical comments some of the time to simple questions, enjoy the rest of it while you can!