Don't worry about it.  The fans come on. So what?

There's probably just something using resources when it detects that the computer is idle.  Antivirus programs, file indexing, scheduled defragmenting jobs, backup utilities, and Windows update all come to mind immediately.  Nothing special about svchost, that's a normal part of Windows for running services, it's just hard to figure out what it's from.

Another update:

I tried not to use my pc for like 15 minutes, and a cmd window appeared saying something about svchost.exe, before I managed to read it, it disappeared. So I think there's something not good going on.

Yes, fans coming on sometimes is good, but not at maximum power exactly after 15 mins after my PC goes idle.

I could confirm to you that this is malware. Svchost itself is legit from Microsoft but there are some common malware that targets it and uses it for their malicious acts. I suggest you do a full scan with Windows defender. This malware could be easily detected because they are so common

This could be the result of a lose internet connection. My pc sometimes does this when networks block special protocols and then these apps keep generating errors while trying to connect. On low powered machines, you sometimes even feel a noticeable impact.

Hmmm I have to handle a lot of older hardware for my family.
One of my uncles in particular likes to buy and use older stuff.
He got one of the latest, well the system before his latest which is actually a good system.
This system as usual was not a brand name hp box or anything but was a cludge of shit some guy put together, slapped some emulation software in to call it a system and put it online.
Well after setting it up, full reformat and everything, it worked, but suddenly things started happening which didn't make sence.
Updates installed but were half done, stuff like sound and things got screwed for no reason.
User profiles corrupted for no reason.
The system got malware and virus like behaviour, even though settings were fine.
Yet, when I had it at my house, did the updates, set everything up, and got it working it wouldn't do.
This went on and on and on, till I decided that it had to be something physical.
Instead of doing what I usually would do, and update it via its wireless interface, I pulled the wireless card from the box and connected it via the network cable.
Immediately the virus like behaviour stopped, software updated fine.
I had to recreate the user accounts and update the mangled sound drivers but a malware check put it as fine and no issues.
The logs though showed several interupted connections and the like.
Firstly, before I say much more, look up ralink or raylink in wikipedia.
Short answer, it doesn't exist anymore.
There is no drivers for any of their stuff and guess what, its not even supported in windows like really much anymore.
You can't even buy their cards anymore.
The card was obviously dead.
I got a large  tp link archer 4t2u which is an ac 1200 card which is quite old now.
However, it at least does work.
Maybe I could have got the miniture but as it is it sits on top of the unit and it runs like its supposed to.
Windows likes to do stuff while it idols.
If it decides to be like that then the windows shell experience is stuck. it often gets stuck here.
One thing you can try, is after installing all updates, and all drivers as well as firmware, follow your computer maker's instructions on flushing theram and other memmory modules.
In most units being desktops with a reset button.
Turn off the unit, pull the plug, take out all the devices.
turn off the switch at the back, hold the reset for 5-15 seconds, then plug the stuff back in slowly, try your keyboard first.
hit the power button and wait.
If nothing happens hit that enter key or f1 or whatever you need to do.
You may or may not need sight to exit setup but most likely you have a boot menu to hit enter on.
It may fix things.
On systems with a power only, same procedure but its the power to hold down for 5-15 seconds.
In laptops hp but maybe others, for the battery ones, remove everything and pull the battery.
then hold power for 5-15 seconds, 15 is suggested.
Without a battery, skip the battery step but the rest is the same pritty much.
I have always had fan noise going nuts.
I did a bios update and also a firmware update and the system couldn't find the boot device  for a few rounds.
It turned out the chips needed a hard flush or powered reset.
If you are lucky, this is probably all you need to do.
My fan no longer does bad things.
It will also refresh your devices if they are not working right.
Certainly things have run a lot better after a powered flush of the chips.
If this doesn't work, resetting bios or a reflash may need to be in order pluss another reset.
But yeah, its something I only just recently found out how to do and its solved a lot of issues.

Yeah svchost is normal, but seeing it pull up command line shit aint. Something's going on that ought not to be.