God chooses Himself when to appear or not. When it's needed. We choose to ask for Him to appear in our personal lifes. Through mircales, blessings, people, the Bible, creation, religeous art and history, all kinds of ways. If you search you will find. Also God appeared to Moses as the biblical story goes in a dark cloud because He is too light and immense to show Himself. And thirdly Jesus said: now that you have seen you believe, blessed those who believe without seeing. So God wants us to believe without seeing, that is what faith is about.
So, God can appear in various ways by willingly choice,to bellieve and search God.