Yes you could, because since you don't train regularly, going out for a 5k run could be very stressful. I've been there, when young 5k was, you could say easy, I could do it any day without warmup or specific training. But now, I can't run 5k without injuring myself. I need to prepare for several weeks before running 5k.

Well sounds like you should train regularly then :)

But overtraining isn’t just getting over exerted and having to rest for a few days or even weeks. It’s a very gnarly condition that’s ridiculously hard to get to. Most of us would mentally tap out long before.

It’s a lot like the difference between needing a break and being burned out. Getting tired and needing a break is normal, being burnt out is a serious condition.

https://en.wikipedia.org/wiki/Overtraining

It happened to me with job and kids. It is very easy to over train or get injury. It does not require hours and hours, just intensity.

And if you had not done sport for a long time and suddenly get back to it, trying to "continue" where you left, that is when injuries happen.

I would guess it also depends on concentration. If you're at the gym exercising a specific muscle group, you could over-exert that muscle easier than generic overtraining while playing a sport.

This makes sense, but I believe it’s incorrect. Overtraining is a fairly serious condition that can take months to recover from, not generic over-exertion of a specific muscle group that requires days of rest.