In Exodus 4, at the birth of his ministry, Moses famously said "I am slow of speech and slow of tongue" when asked by God to lead the children of Israel out of Egypt. He had already told God that no one would listen to him, and God responded by giving him the power to do miracles.
But when Moses still doubted his ability to speak and lead, God rebuked him, saying, “Who has made man’s mouth? Or who makes the mute, the deaf, the seeing, or the blind? Have not I, the Lord? Now therefore, go, and I will be with your mouth and teach you what you shall say.”
But yet again, Moses lacked faith in God's ability to enable him for service and begged God for someone to help him. God relented, giving Moses his articulate brother Aaron as a spokesman. This second choice did not always bode well for Moses, though, such as the time when he went up to Mount Sinai for a 40 days and 40 nights as the Lord spoke many things to him and the children of Israel meanwhile easily followed his spokesman Aaron into committing idolatry by worshipping a golden calf.
Who else in the Bible was noted as not being a good speaker?
The Apostle Paul. In 2 Corinthians 11:5-6, he admits, "For I consider that I am not at all inferior to the most eminent apostles. Even though I am untrained in speech, yet I am not in knowledge. But we have been thoroughly manifested among you in all things."
Despite his lack of ability, Paul was a willing servant that God empowered mightily. Luke noted in Acts 28:31 that Paul spoke "with all confidence" as he preached the Good News.