Can I preach for the sake of Allah while I am not knowledgeable in religion, especially with my fear of encountering شبهات (misconceptions/dubious matters) that I may not know how to respond to, and how can I balance the desire to preach with a lack of religious knowledge?

It is prescribed to invite people to the religion for anyone who knows something about it, no matter how young they are. It is obligatory to invite atheists, obstinate individuals, and those with doubts, for anyone who is armed with knowledge, out of fear that a doubt might be cast that enters the heart. It is recommended to supplicate for steadfastness and success in inviting to Allah with wisdom and good admonition.