Q: Mac Mini won't boot up, just beeps once every 4 seconds. Is it dead?

Which tone:

• 1 tone, repeating every 5 seconds: This indicates no RAM is installed.
• 3 successive tones, a 5 second pause (repeating): This indicates RAM does not pass a data integrity check.
• 1 long tone while holding down the power button: Indicates an EFI ROM update is in progress on a computer manufactured before 2012.
• 3 long tones, 3 short tones, 3 long tones: Indicates EFI ROM corruption is detected and the computer is in EFI ROM recovery mode.

Mac computers: About startup tones - Apple Support

Sounds like a RAM problem:

• 1 tone, repeating every 5 seconds: This indicates no RAM is installed.

Try reseat8ng the RAM. Finde you Mac here for how to access the RAM

Or you can

Make an appointment at the Genius Bar of an Apple store. No warranty required

  Apple Retail Store - Genius Bar