Mac freezing up and logging me out

Hi,

I recently bought a Macbook Pro and everything has been fine until the last few weeks.

The computer has started 'crashing'. I'm not really sure what else to call it. I noticed the problem a few times over the last couple of weeks, always somewhat erractically. I would go off and do something, and come back to find that I was back on the user sign-in screen.

However, in the last couple of days, this has happened while I'm actually using the computer. It's happened twice, and both times I was browsing on the Internet. Everything froze, and after a long pause - I didn't time it, but I would guess 20 seconds or so - I was kicked out and back to the user sign-in screen.

I'm on a Macbook Pro, 13-inch, 2020 edition. I'm running Monterey, 12.1.

I've checked, and I don't seem to need an update (Pages, Numbers, and Keynote needed updating, but those were the only ones I could find).

A quick scan with Avira says no viruses.

Maybe I'm overreacting, but I don't really have the money to replace my laptop, and I have, until now, been absolutely thrilled with it.

Any help hugely appreciated.

Thank you