Albert Barnes Commentary Psalms 119:120

"My flesh trembleth for fear of thee; And I am afraid of thy judgments. AYIN." — Psalms 119:120 (ASV)

My flesh trembles for fear of you—I stand in awe of you. I shudder at the consciousness of your presence. See (Habakkuk 3:16); (Hebrews 12:21); (Joel 2:10); (Nahum 1:5).

There is nothing unaccountable in this. Any man would tremble if God were to manifest himself to him as he might do; and it is possible that the mind may have such an overpowering sense of the presence and majesty of God that the body would be agitated, lose its strength, and with the deepest alarm fall to the earth. Compare (Daniel 10:8); (Revelation 1:17). No man could meet one of the departed dead, or a good angel, without this fear; how much less could he meet God!

And I am afraid of your judgments—Of your laws or commands. My mind is filled with awe at the strictness, the spirituality, the severity of your law. Reverence—awe—is one of the essential elements of all true religion.