Are you using Jupyter notebooks? They continue to run, even when you're not viewing them, and when they're idle they "sip" CPU power at a rate of about a second per minute. In the processes table at the bottom of the Consoles page they'll have names like "jupyter", "sudospawner", or "kernel". It can be a bit tricky to spot that they're using up the CPU because they do it by spawning a new process, which uses up about a second, then exits -- the parent process that's doing the spawning doesn't use up much CPU by doing that, and of course the processes that start then stop are very ephemeral, so you will probably not see them.