Is it possible for a clause to be reduced when it uses the verb "to be"? Here's an example sentence:
When I'm lazy, I usually sleep.
Can I reduce the when clause here to:
When being lazy, I usually sleep.
If the meaning is clear, we often leave out words in conversation. It's called ellipsis.
So, you can even omit "I'm" or "being' and say "When lazy, I usually sleep." Please note that the sentence is informal now, unlike "When I'm lazy, I usually sleep", which is neutral.