John Gill Commentary Daniel 2:29

"as for thee, O king, thy thoughts came [into thy mind] upon thy bed, what should come to pass hereafter; and he that revealeth secrets hath made known to thee what shall come to pass." — Daniel 2:29 (ASV)

As for you, O king
So far as you have any concern in this matter, or with respect to you, the following was your case; these the circumstances and situation in which you were.

Your thoughts came into your mind upon your bed, which should come to pass
hereafter; as he lay on his bed, either sleeping or waking, very probably the latter, his thoughts were employed about this great monarchy he had erected, and what would be the issue of it; and was very desirous of knowing what successors he should have in it, and how long it would continue, and what would be the fate of it; when he fell asleep upon this, and had a dream agreeable to his waking thoughts.

And he that reveals secrets: a periphrasis of the God of heaven, as in the preceding verse.

Makes known to you what shall come to pass; this he did by the dream he gave him, though he had forgot it; and now by restoring that, and the interpretation of it, by Daniel.