I'm sorry but the description "turning in" isn't terribly helpful - can you describe what's happening better, or better yet, post a photograph with your question?

if it is an evergreen it could literally be curling in due to the cold.

I suspect SBG has hit the nail on the head. We have lots of shrubs in the garden where the leaves are either pointing downwards (rhododendrons) or have pulled into themselves. Natural reaction to the very frosty weather - will recover once it is warmer.