Sometimes when you join two words together to form a new word, the meaning changes. For example, "every day" and "everyday" do not mean the same thing at all (and they sound different as well). However "sometime" and "sometimes" pretty much do mean the same as "some time" and "some times". So, the difference is just that between singular and plural.

Sometime means “at some point.” As an adjective, sometime also means “former.” Sometimes means “occasionally.”

'Sometime' means a point in time but not an exact time or decided time. For example, 'We must get a coffee together sometime'. 'Sometimes' means occasionally. For example, 'I sometimes go running'.