When you do not know what to say
Prayer is not a performance. Start with one honest sentence.
You do not need the right words. God already knows what is on your heart, and he is not grading your prayers. Prayer is simply talking with someone who loves you.
If you are stuck, start with one honest sentence: "God, I do not know what to say." Then tell him what is true right now: tired, afraid, grateful, angry, confused. He can handle all of it.
When words will not come, the Bible says the Holy Spirit prays for us with groans too deep for words. You can sit in silence for a minute and let that be your prayer.
Read and pray these
26In the same way, the Spirit also helps our weaknesses, for we don’t know how to pray as we ought. But the Spirit himself makes intercession for us with groanings which can’t be uttered. 27He who searches the hearts knows what is on the Spirit’s mind, because he makes intercession for the saints according to God.
8Trust in him at all times, you people. Pour out your heart before him. God is a refuge for us. Selah.
7In praying, don’t use vain repetitions as the Gentiles do; for they think that they will be heard for their much speaking. 8Therefore don’t be like them, for your Father knows what things you need before you ask him.
Scripture quotations are from the World English Bible (WEB), public domain.