With this particular expression, it really doesn’t matter whether you use the continuous aspect of the simple aspect. The continuous aspect strikes me as a bit stronger, but it’s only usable if you are referring to a current action. The simple aspect will always work with this verb, and is usually the best option if you’re referring to something more general (often with an adverb of frequency such as “usually”, “always”, “never”, etc.). The simple aspect is guaranteed to be grammatically correct (with this particular verb). A grammatically similar expression is “I’m wondering” / “I wonder”.

Both depending on context. I am looking forward to hearing from you. I look forward to hearing from you. The first version has more emphasis.