B2 sometimes but not often:
- The path follows the river closely, occasionally deviating round a clump of trees.
- You're bound to forget people's names occasionally.
- She only sees her niece occasionally, so she showers her with presents when she does.
- Does it never occur to you that I might like to be on my own occasionally?
- I don't mind helping her out occasionally, but this is getting beyond a joke.