Getting stuck in essentially a boot loop is typically a bad situation. The first thing you should try is boot up your phone into its Safe mode:
https://www.hardreset.info/devices/samsung/samsung-galaxy-a54/safe-mode/
If you phone boots up properly in Safe mode that's an indicator some app you've installed is the source of your problem. When running in Safe mode that's just the base Android operating system, and no other, third-party background services get loaded into memory at boot up. Of course now you have the daunting task of finding just which app you've installed is the culprit but it's a start. Also, with Safe mode you're not deleting anything so it's a non-destructive task.
If Safe mode doesn't work out, then try booting up into your phone's Recovery mode and do a Factory Reset:
https://www.hardreset.info/devices/samsung/samsung-galaxy-a54/
Keep in mind a Factory Reset will wipe your saved data so hopefully you have previously set up a full backup solution of some sort. If you didn't, you're going to lose data. Your phone's Google-related data and settings will likely be OK as that resides primarily in your online Google account by default, and a lot of Samsung-related data and settings in its own branded, online account, but things like documents, audio files, and other random personal data might be in question.
If a Factory Reset doesn't restore your phone back to working condition, a last resort measure is to flash a stock Samsung ROM, flashing the ROM (a.k.a reinstalling the firmware) will replace the otherwise 'damaged' current Android operating system with a clean Android OS:
https://www.sammobile.com/samsung/galaxy-a54-5g/firmware/
Go the site above, and be sure to choose the proper ROM. They are not interchangeable so be sure to pick your specific phone's model I.D. (i.e. SM-A546U or SM-A54V or whichever), and then your carrier. Don't mix and match, it's vital to choose the specific firmware. Once you select it, a download page will show, and links to directions on how to do the flashing.