I opened a couple bottles I purchased on auction and both were sour/astringent. I set them aside to revisit in 1-2 days but I’m not confident they will be any better. Is this what overheated wines taste like or is it more likely that these are just bad bottles?
I think of a sour taste as an oxidized wine. I think of a more stewed taste for heat damage.
“Sour” is so vague term that it doesn’t mean anything. Normally “sour” is synonymous with something that is acidic, so in that sense all wines are “sour”. Although many people say “sour” only if a wine is too high in acidity, ie. the acidity sticks out. Nothing to do with cooked wine.
Astringent basically means the same thing as tannic. Again nothing to do with cooked wine. Normally wines that show heat damage or oxidation tend to lose their tannins, so if anything, a cooked wine shouldn’t be astringent.
Just as Paul said above, if a wine has enough heat damage to be cooked, usually there’s a stewed taste and the flavor profile turns pruney / raisiny.
Oxidation normally means buildup of free aldehydes (which normally get bound by sulfites). When a wine starts to show oxidation, the free sulfites are depleted and you start to both smell and taste the aldehydes, resulting in an oxidative character in wine. Although sharp / pungent, I personally wouldn’t describe aldehydes as “sour”, but this certainly can be it.
However, you most certainly can have a wine that is both heat damaged and oxidized, since chemical reactions accelerate as temperature goes up, so a wine that has been kept too long in too warm temperature oxidizes faster, depletes its free SO2 at a faster rate and starts to taste oxidized. In room temperature the wine normally doesn’t develop develop any cooked flavors - at least not in many, many years - but in above room temperature a wine definitely starts to develop cooked flavors. A wine that has been kept for a short time in hot temperature (like a day in a car that’s been sitting under summer sun) might show a lot of cooked flavors but no oxidative qualities.
A wine can always be slightly corked so there is no fruit to speak of, making the acidity and tannins stick out badly (and in this kind of instance a wine could be described as “sour and astringent”), but if the problem is with two bottles, that sounds unlikely.
It might be helpful to name the wines
Yes!
Excellent point, it could be some really young, cool kid, whole cluster Burgundy and taste sour 
2018 Krug Generations
2017 Shafer Relentless
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Were the nose on either off putting? Usually cooked wine has a disjointed nose, like it was broken down into parts and not meshing.
BTW, those are young wines, and would be a bit weird if they were cooked. Not saying it’s not possible, just taking note.