I will always say the beginning of autumn semester and spring semester are completely different. Before autumn semester you're getting ready for an entire year of school, professors are sending emails a couple weeks in advance, organizations are recruiting, and overall you're taking a longer time to prepare for what's ahead.
Spring semester creeps up on you a little better.
The week before spring semester you almost forget you have school coming up. You haven't really heard from any professors because everyone's been celebrating the holidays and you barely remember what classes you're even signed up for. Instead of spending weeks preparing for everything to start, you spend a few hours the day before classes. Overall, spring semester just hits you with everything because you're going straight from holiday-mode to school-mode and that's not a smooth transition.
Another facet of spring semester it that it moves faster than autumn semester from the get-go. At the beginning of the school year, most people have had a few months off from learning. Spring semester you're supposed to be used to school again so you're expected to hit the ground running.
Needless to say, I'm trying to switch out of that holiday-mode and remember that I still have a semester of undergrad to get through, along with working and helping run a club. Having to get up early again will be a rude awakening (literally) from relaxing over winter break.
While the start of spring semester may be overwhelming, just remember that it's also the start to a brand new year, which means it's the perfect time to change some of the bad habits you got into at the end of last semester. Fix your sleep schedule, stop procrastinating, and make more time for self-care - maybe the start of the semester won't be so bad.