When can I call you sometime?

"When would be a good time to call you?"

"Could I give you a ring at some point, and if so, when would be a good time?"

"Perhaps I could give you a call at some point, if it's convenient?" (hier ist die Frage nach der Zeit eher impliziert).

Todd's Vorschlag klingt für mich (BE) leider überhaupt nicht idiomatisch.

#1: That's an awkward combination, I'd say. It's usually either "When can I call you?" or "Can I call you sometime?"

It is kind of awkward, but if forced to use one sentence to convey that you want to call but not right away, that's how I'd do it. Probably would only work when speaking. I wouldn't write that.

Teenager speak: Could I like, you know,umm, maybe call you sometime?