We tried reaching you on a private message asking for the Service Tag number to ascertain the warranty but did not receive a response. Please feel free to reply to the private message whenever you are available.

Hello,

as a private message I have sent all data to start talking with a real person - I hope on your reply.

1 3 4   Diagnostic LED's

A possible sysem board resource and/or hardware failure has occurred.

Clear CMOS (replace the coin-cell battery.)

Disconnect all internal and external peripherals, and restart the computer.

If the computer boots, add the peripheral cards back one by one until you
find the bad one.

https://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprtl_precision_workstation/precision-t3600_owner's%20manual_en-us.pdf

The T3600 was introduced 9 yrs. ago.  If not in the last 5 yrs., try replacing the size 2032 CMOS battery first.