How are you measuring temperature? Use HWInfo64 and look at the CPU Die (average) temp. The temps that spike around can be a bit misleading as the spike is from when the CPU boosts to a high clock from idle so it's not the real temperature.
But that said, Ryzen 5000 does run a bit hotter and 58C isn't all that hot yet. I'd be more worried what's happening under stress: run CB23 and look at the temperature then. It will run for about 10 minutes so you'll get a good idea what it's like under real-world AVX-heavy workload. It's not unexpected for a 5600X
to get up to 90-95C in such a load but I'd expect a 240mm AIO to keep that in check.