I do not think it is normal to feel nervous, but I think it shows quite a sophisticated and sensitive reaction. When we think seriously about heaven, its glories, and the holiness of God, it is an appropriate reaction to think, “In all of my sinfulness, how can I stand before a holy God?”
One of R.C. Sproul’s favorite texts was Isaiah 6, where the angel declared the holiness of God, “Holy, holy, holy,” and the prophet Isaiah was privileged to see God in His holiness in the heavenly temple. His response was very proper: “Woe is me, I am undone. I am a man of unclean lips” (Isa. 6:5). To be intimidated by the holiness of God and the splendors of heaven is an appropriate response initially, but we should not stay there.
God has sent His Son so that we might have confidence, that we might know ourselves to be the children of God and have boldness of access into the Father’s presence, as Hebrews teaches. There is a kind of back and forth in the Christian experience as we really think about our sinfulness. It may remind us of the holiness of heaven and trouble us, but we have to keep coming back to Christ.
Something John Calvin does so well is bring us back to Christ and constantly assure us that Jesus came to reconcile us to the Father. Jesus came to assure us that we belong to God and have peace with God, not that we will have peace with God, but that we already have peace with God and the right of bold access to the Father.