Confusion hits us all sometimes, so what brings this on astrologically? Neptune, of course! Neptune clouds our judgment, brings in the haziness and fog, and makes it hard to figure out what's really happening. So when transit Neptune is making a hard aspect (conjunction, square, opposition) to any of your natal planets or house cusps, you can suffer from some major confusion. It can last for a while too, because transit Neptune doesn't move very fast, so you can be under the fog of confusion for some time (months at a time over a couple of years!). It's always important to ground yourself and work on being as realistic as possible with Neptune transits, and this can help you to avoid getting too confused. But, you probably can't escape it all.
You can also suffer from confusion when you're experiencing a hard transit aspect to your natal Neptune. With the Sun, Mercury, Venus, and Mars, this only lasts for a few days, so you get a shot of some confusing energy briefly. Those days aren't great for scheduling important decisions, tests, or anything that requires focus or discipline. The Moon aspects your natal Neptune for just a few hours, but that can be a period where you're head is completely in a fog and you can't see anything straight.
With Jupiter, this can last for a couple of weeks, and the confusion, the haziness, and the fog can be even bigger with him since Jupiter energy is expansive. You definitely want to avoid anything that requires focus because that is very hard to find. With Saturn, this can last for several weeks to a couple months, and Saturn is the planet of reality, so you can be super realistic to the point of lacking any and all imagination, or you can be super unrealistic to the point of being delusional and constantly confused. Balance is required here.
With Uranus, this can last for several months, and you may have sudden bouts of confusion, or confusion may lead to some developments that are sudden or out of your control. With Pluto, this can last up to 3 years, and the confusion can make you vulnerable to bad people, so you have to be careful of who you're around.
Neptune rules the 12th house, so you can also suffer from confusion when you have hard aspects to your 12th house cusp or ruler, and you can be more prone to confusion when transit planets are touring your 12th house. You can This can be confusion in general with the Sun, mental confusion with Mercury, emotional confusion with the Moon, confusion in your relationships with Venus, confusion about taking initiative with Mars, confusion with where to expand with Jupiter., or confusion about changes with Uranus. Saturn in the 12th house can tamp down confusion and make you more realistic. Pluto in the 12th house can also bring in more reality, though confusion can also lead to deeper problems.
When you know you're under the influence of a hard Neptune transit or hard transit to your natal Neptune, make sure you're checking in with yourself a lot, and work on getting grounded.