Macbook Pro during start up will chime, Apple will appear but the load bar indicates that it will only load about 60%, then the screen goes black and the cycle retarts over and over again; HELPP

Reinstall El Capitan or Later Without Erasing Drive

Please be sure you back up.

1. Restart the computer. Immediately after the chime hold down the Command and R keys until the Utility Menu appears.
2. Select Disk Utility and click on the Continue button.
3. Select the indented (usually, Macintosh HD) volume entry from the side list.
4. Click on the First Aid icon in the toolbar. Wait until the Done button activates, then click on it.
5. Quit Disk Utility and return to the Utility Menu.
6. Select Reinstall OS X and click on the Continue button.
7. Test to see if the problem is gone.

Also, see this User Tip: Basic Steps for Upgrading OS X.

Clearly, the second procedure does as it says - Erases the drive then installs OS X.

Use Activity Monitor to Kill Runaway Processes

Use Activity Monitor on your Mac

Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity.

Should the above not prove helpful, then make an appointment at the Apple Genius Bar for service. If you need to find an Apple Store - Find a Store - Apple.

In that case, you will need to erase and install. Important that you have your files backed up.

Install El Capitan or Later from Scratch

Backup if possible before continuing.

1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
2. Select Disk Utility from the Utility Menu and click on Continue button.
3. When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
5. Set the Format type to Mac OS Extended (Journaled.)
6. Click on the Apply button, then wait for the Done button to activate and click on it.
7. Quit Disk Utility and return to the Utility Menu.
8. Select Reinstall OS X and click on the Continue button.