Thanks girls will bring him to docs and get referral to have it checked out. They might ask me to keep record as to how often it happens so will see what they do straight away.

Will keep you posted Taurean.
No particular textures or food that triggers it Chocoholic just random. Last night was shepherds pie and before that was piece of apple. Hadn't happened for ages but twice recently which prompted me to post.

Fingers crossed there is nothing wrong - feeling slightly worried now.