Macbook pro 2015 keeps resetting and doesnt go pass the intially loading screen.

how to proceed:

restart in Recovery mode (command R). Launch Disk Utility and Repair disk. if any errors, repair again until it is fixed or is stuck doing the same thing every time.

Stuck:

IF you have adequate backups, so that a copy of your files will be available later, you can erase the drive and re-install macOS. you may need to install the 'Shipped in the box' version, start it up and create an account, let it settle its initial hour of cleaning up, then enter and activate an APPLE-ID before it will allow you to upgrade to the version you were running before.

if you do NOT have adequate backups, changing settings to allow booting from an EXTERNAL drive, then installing MacOS on that External drive and running from the external drive can allow you to salvage files off the damaged internal drive. (Mounting for reading is a far simpler requirement than booting off a drive.)

Remember the goal is your files, not a brute force copy including macOS, which can be reproduced with complete accuracy by a re-install.

the underlying problem:

The initial "chime" sound is generated in software when your Mac passes the Power-On Self Test. If the chime occurs and/or startup continues, your Mac is working. The screen should light up and draw a blank gray screen. Then on to the Disk Drive.

Accessing the Boot drive:

The solid Apple is not in the Mac's ROM at Cold start. The Apple logo can only appear when it is fetched in the first "blob" of software loaded from a 'magic' place on the boot drive, or re-run after a Restart. Then a whole lot of stuff is initialized, and the progress Bar moves part way across. After a cold start, seeing the solid Apple appear says your drive was able to produce the software that contains the Apple logo.

If a prohibitory sign appears at this point, it indicates some fundamental part of MacOS is damaged or wrong version.

Mounting the Boot drive:

The next step requires a lot of files by name, so the File System is initialized, and the Boot Drive is Mounted. If the drive directory is damaged, the drive can not be Mounted, so your Mac begins one pass of Disk Utility Repair. This will take an additional about five minutes. During this process, the progress bar may be extended, and will grow by an additional amount not seen on a routine startup.

at the end of that process (which should not take more than about five minutes), it will attempt to Mount the drive again:

-- if the drive Mounts, boot-up continues.

-- if the drive cannot be Mounted, your Mac can do nothing more, so it powers off.

-- if the process stalls, this may indicate you have Bad Blocks on your Rotating Magnetic Boot drive (if so equipped). The re-reading of Bad blocks can take a very long time (on the order of a quarter minute for each Bad Block).