The problem is that our thinking is surrounded by all kinds of boxes that limit our ability to conceive things. This derives largely from our experiences when we are babies and learning the physics we need to know to avoid injury (such as "down" is dangerous, as is fire).
Almost everyone sometime around third grade goes through a period of wondering about people on the other side of the globe falling off.
One of the strongest lessons we learn as babies is causation -- that very very often when A happens it is always followed by B. Stick your finger in a fire (A) and it burns (

. It takes a great deal of unlearning to know that this is not always the case and that two events happening one after the other, even over and over and over, does not necessarily imply any kind of causation (hence medical science requires placebo and double-blind tests and statistical analysis).
Hume made it clear, with close analysis of cases where causation seems undeniable, that the situation is really much more complicated, and that what you tend to have when you look at such things closely is an infinite regression of smaller and smaller associations that in the aggregate add up to what we perceive as causation. He made it clear that what we call "causation" is a mental conclusion we draw when events seem to be tied to each other, but that we are not to draw any certainty that the next time we try it will happen again -- only that it probably will happen again.
That the universe had a beginning in time (that is, has not always existed) seems mathematically necessary (how did the universe get from infinitely far away to here?) and that this beginning was utterly uncaused is inescapable. (Assuming a creator existing from infinity solves nothing).
There is a tendency to want to think of the beginning of time as happening in some sort of "super-time." That would not be correct. There is no such thing as "before" the beginning of time any more than there is a "north" of the North Pole. There is no eternity to worry about -- the beginning of time is the beginning.