High in the sky, moving “slowly” from west to east, bright spot of light, periodically changing the brightness

There was no trail. I think the source of light is sun reflection but it could not be an aircraft because it was pulsating, like it was slowly spinning, changing its form which created a different degree of sun reflection, approximately every 10 seconds. It could be ISS obased on its orbit, or big satellite, but I guess it’s still too big and too bright to be seen in Texas at 10 am in July, with clear sky. It disappeared when it crossed the zenith point half way through the sky towards east (which I guess also points to the fact that the source of light is sun reflection).