> This system has been showing auto shutdown symptoms [...]

   What, exactly, are "auto shutdown symptoms"?  Orderly shutdown? 
Spontaneous, abrupt power-down?  ...?

> Upon startup the system runs through the 4 LEDs on the front panel,
> then after a few seconds on the last one (the one all the way to the
> left) it shuts down.

   Define "upon startup".  Do you mean power-up?  Define "shuts down". 
Do you mean powers down (spontaneously)?  Do you have a console terminal
connected to the system?  Any output there?

> [...] Im wondering if there is either A) a temp sensor that has failed
> or B) a memory issue.

   I've never touched a DS25, and I don't have the hardware manual for
one (do you?), so I know nothing, but I doubt that any likely memory
problem could cause a spontaneous power-down.  (How much memory is in
the system?  Remove half?  Replace it and remove the other half?)  A
failed temp sensor seems even less likely to trigger a spontaneous
power-down without generating a console message first.

> [...] in the midst of troubleshooting the system was restored [...]

   Do you mean that it started working properly, or that you did a
BACKUP?

> [...] one of the errors that came up mentioned the CPU fan 1. [...]

   What were the other errors?

   Knowing nothing, I'd suspect the (old) power supply, but I can't see
any diagnostic LEDs which might be on the system main board, I see any
console terminal output, and so on.

   If the system is under a hardware maintenance contract, then I'd
demand some actual service.  "Started working spontaneously" is not the
same as "was repaired".  If the problem comes and goes, then I'd expect
to get the system replaced, so that I could get some work done while
someone else tries to figure out where the real problem lies. 
Otherwise, what are you paying for?