Question:
Is being shy a stumbling block when I witness to my friends?

Answer:
It need not be, and will not be, if we have our hearts taken up with the Lord and what He has done for us.

The apostle Paul said 2 Timothy 1:12: “For the which cause I also suffer these things: nevertheless I am not ashamed: for I know whom I have believed, and am persuaded that he is able to keep that which I have committed unto him against that day.”
If you are a Christian you probably have had the experience of being ashamed or afraid of telling people about the Lord, but Paul wasn’t ashamed because he knew “Whom” he had believed. It is important to know the Person of the Lord Jesus, “Whom” you have believed, and be persuaded that He is able to keep your soul, or you will be ashamed to live for Him.
Let each of us ask ourselves: “Am I persuaded that He is able to keep my soul?” If we are not persuaded it is because we do not have faith in Him and His Word. This is sin, and sin blocks communion with God.
Ask the Lord like David did: “Restore unto me the joy of thy salvation; and uphold me with thy free spirit. Then will I teach transgressors Thy ways; and sinners shall be converted unto Thee” (Psalm 51:12, 13).