I'm planing on playing a Warforged Cleric and recently got a voice mod to help with roleplaying. But I'm unclear as to how exactly a warforged would sound.

Would it be completely robotic or something like zenyatta? Or maybe something human with a metallic sound coupled with it?

The Races of Eberron 3.5 book calls out their voices as "hollow and monotonal", but that's mainly due to the fact they were created to be soldiers and were given a vocabulary and manner of speech that is clear and consistent on the battlefield. Their ability to speak is more through magic than by mechanical means, so they can sound however you want them to sound.

That makes a lot of sense! I'll give it some practice.

Baymax from Big Hero 6.

I went with more of a Commander Data kind of voice for my juggernaut eldritch knight; soft spoken despite great strength, cautious, curious, but in an almost-natural sounding monotone. In moments of intense negative emotion however, the almost-human-sounding quality fades away to sound more mechanical

I’m playing a warforged in my campaign and have been playing around with different sounds. The default I’ve inadvertently landed on sounds like K2SO from Rogue One. Kind of British/Mid-Atlantic sound like a 40s movie actor but not as over-the-top. 

I play a warforged druid and tend to go for a low, creaking effect to my voice, more like old wood than anything electronic or mechanical, although it can sound a bit monotone.

They always remind me of Alphonse Elric from Fullmetal Alchemist, so I imagine a fairly regular voice coming from the middle of a hollow shell and having to reverberate its way out.

When I played a Warforged Paladin (who was built to protect a 6 year-old girl) his voice was kind of lighthearted and singsongy. Of course, he was a couple of McNuggets short of a Happy Meal. 

Think Caboose (of RvB) met Grog.

I'd be curious what voice mod you have, and how you end up liking it.  I think it would be fun to do something like speaking without inflection and  having to state your tone verbally like the Elcor in Mass Effect.   Might also be really annoying though, ha; 

calm and warm like a docter or nurse

I literally used Star Trek computer sounds and other sound effects from my laptop.  I have dozens organized by use. He's a Warlock whose patron is The Eye (i.e. AI). He originated as an NPC I created for a alternate 5e version of Expedition to the Barrier Peaks in my Greyhawk campaign. Really fun PC.

Baymax would be funny It goes up to a  PC with only 3 hp left " Do you require medical attention, On a scale of one to ten, how would you rate your pain?”

Shale/Shayle from Dragon Age: The Stone Prisoner (Geraldine Blecker) or Harvey Fierstein.

If you happen to know destiny, there a race call the exos that are quite similar to warforged, most notable exos are Cayde-6, Banshee-44, Shiro-4, Taeko-3 and the Exo Stranger and the player character who chooses to be an Exo but they have little dialogue.

They sound like those text to speech softwares

(I originally meant this as a joke, but then i realized that it would actually make sense) 

I have a character who's a warforged druid (haven't used him yet but I really want to). He speaks mostly in single words and sentence fragments, he has a russian accent, and his voice sounds, deep, a bit scratchy, and almost pained at times. I have no idea how these disparate elements came together or why I ever thought they made sense. 

or calm and no nonsens like rachet from transmormers

I have been experimenting with the voice mod, but not yet happy enough to use as a DM

However, I used a cup on a mic, and tried to sound like a monotone version of "Goblin Slayer" (Japanese, not the English dub)