When idling, laptop runs background programs with 'Very high' power usage, leading to loud fans

I have an Acer Aspire 7 A717-72G-700J laptop which is now a couple of years old and which runs Windows 10. Oftentimes, when I leave it idle for a few minutes, the fans start whirring, and when I check Task Manager I find that one program or another is running in the background, leading to 'Very high' power usage, which is presumably what's causing the fans to run. Some culprits include:

• MsMpEng.exe / Antimalware Service Executable: this is probably the one that causes this most frequently. I presume Windows Defender is running some sort of background scan, but when I open up Defender it doesn't say anything about it currently running a scan, and usually the last scan recorded was hours ago, or even the previous day.
• Google Chrome: I sometimes have quite a few tabs open, but I'm not actually doing anything on them, and they shouldn't be running anything in the background (it's often just reddit, Wikipedia, or other websites that are 99% text), yet, while idling, Chrome will leap to 'Very high' power usage.
• AggregatorHost.exe
• msedgewebview2.exe: I don't even use Edge!

I think wsappx and some others may have caused problems as well. To be honest, I've kind of lost track at this point, since it happens so regularly.

If anyone knows how to fix this I'd really appreciate. I've Googled this previously and it seems like lots of others have this problem too, especially with the Antimalware Service Executable one, but fiddling with Defender settings hasn't fixed things, and because I'm having it with loads of different programs I'm beginning to think it might be a broader problem.