Repeated suspicious activity on Gmail
Two weeks ago I got notified on my phone that there had been suspicious activity on my gmail on a windows computer. I was using email on my Windows just moments earlier, and there is only one windows-session on my active devices on Gmail. Gmail said that it had logged out of the suspicious device, and it had in fact logged me out on my computer.
I scanned my computer with Microsoft Defender and Safety Scanner, which did not find anything. I then changed passwords on a trusted device and logged out of all my gmail sessions on my computer for a while.
A day or so after I logged back in, I got the same suspicious activity notification again, but for a different account I have. I again repeated the previous steps, and in addition scanned also with F-Secure and Malwarebytes, while finding nothing.
What is going on? I need to use the computer but I don't trust that everything is okay.