To oscillate and to repeat - Meaning is similar, but not the same.
Oscillation does repeat, but it doesn't simply mean to repeat.
Oscillation is repetitive variation (or predictable, repeating, change) between two (or more) states.
Example:
To repeat, is to happen, again and again. To oscillate, is to change, to change back, and to repeat, again and again. Oscillation is a cycle of repetition.