I really believe there was a concept of Trinity held by some Hebrews before the birth of Jesus Christ like this ex. from the book of Enoch: (see passsage 48:2, I tried to bold (but could not) the terms,"Son of Man", "Lord of spirits", & "Ancient of Days". The translation is the 1st English translation done by Anglican Bishop Richard Laurence & some have disputed parts of his translation like this one but yet it is accepted as overall sound but the pre Christian aspects just cannot seem to be true according to critics (sigh).
Enoch Chapter 48
Enoch 48:1 In that place I beheld a fountain of righteousness, which never failed, encircled by many springs of wisdom. Of these all the thirsty drank, and were filled with wisdom, having their habitation with the righteous, the elect, and the holy.
Enoch 48:2 In that hour was this Son of man invoked before the Lord of spirits, and his name in the presence of the Ancient of days.
Enoch 48:3 Before the sun and the signs were created, before the stars of heaven were formed, his name was invoked in the presence of the Lord of spirits. A support shall he be for the righteous and the holy to lean upon, without falling; and he shall be the light of nations.
Enoch 48:4 He shall be the hope of those whose hearts are troubled. All, who dwell on earth, shall fall down and worship before him; shall bless and glorify him, and sing praises to the name of the Lord of spirits.
Enoch 48:5 Therefore the Elect and the Concealed One existed in his presence, before the world was created, and for ever.
Enoch 48:6 In his presence he existed, and has revealed to the saints and to the righteous the wisdom of the Lord of spirits; for he has preserved the lot of the righteous, because they have hated and rejected this world of iniquity, and have detested all its works and ways, in the name of the Lord of spirits.
Enoch 48:7 For in his name shall they be preserved; and his will shall be their life. In those days shall the kings of the earth and the mighty men, who have gained the world by their achievements, become humble in countenance.
Enoch 48:8 For in the day of their anxiety and trouble their souls shall not be saved; and they shall be in subjection to those whom I have chosen.
Enoch 48:9 I will cast them like hay into the fire, and like lead into the water. Thus shall they burn in the presence of the righteous, and sink in the presence of the holy; nor shall a tenth part of them be found.
Enoch 48:10 But in the day of their trouble, the world shall obtain tranquillity.
Enoch 48:11 In his presence shall they fall, and not be raised up again; nor shall there be any one to take them out of his hands, and to lift them up: for they have denied the Lord of spirits, and his Messiah. The name of the Lord of spirits shall be blessed.