"I'm thinking of" vs "I'm wondering" vs "I wonder"

When we want to say that we have been thinking (for days) before taking a decision, I'm use to saying

I'm thinking of hiring another employee...

Are there any other ways of saying the same thing?

I wonder hiring another employee...

By the way, is that right saying I'm wondering?

"I am thinking of hiring another employee" is the right expression. It suggests that one is reasonably aware of the need to hire. There are 30900 results when I google the full sentence.

"I wonder hiring another employee" sounds incomplete. The sentence - "I wonder if hiring another employee is worth it" - will be a coherent message, i.e. you are unsure of it. One of the meanings of 'wonder' according to dictionary.com is "to feel doubt"