Why does it power on 3 times?  Is the hard drive clicking just a symptom and not an actual problem?

Welcome to the Dell Community @supertrucker39 

Try re-seating the memory first.

If that does not work then try this.

Disconnect the CMOS battery and then try to boot.

Dell Latitude E6420 and E6420 ATG Owner's Manual:

https://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_latitude_laptop/latitude-e6420_owner%27s%20manual_en-us.pdf

With the CMOS battery disconnected connect the AC adapter.

It should try to power-on by itself. "Up to 3 times"

Best regards,

U2

@supertrucker39 

Disconnecting the Coin Cell battery clears the CMOS.

After connecting the AC adapter it will automatically try to power on.

But it could take up to 3 times to do so.

After this the BIOS/CMOS battery can be re-connected.

The hard drive clicking is caused by the Head Stack Assembly going out to read the platters and doing an emergency park because it ran into a problem.

Hence the clicking sound. 

That is a good indicator that the HDD has failed.

Regards,

U2