My 4yo is repeating the last sound of words. not every sentence, but several times a day. for instance cake...k..k.. or animals...s..s. normal?

Can be: Secondary stuttering in a kid who didn't before can be a transitional stage that lasts a few months. 3-4 would be a common time for it to appear. After a few months it usually fades. Letting the kid self recover & ignoring the error helps them more than stopping them and pointing out the error. They are aware & usually self conscious. If it persists see a speech pathologist.