Aiming problems?

Merry christmas!
I needed help because I have just reinstalled Gmod on a new computer, and while walking or in the Q menu I cannot move the mouse. Basically I can aim normally but NOT whilst walking, so I have to stop, wait a few seconds and THEN readjust the aim. To use the Q menu I have to open it, press a key and then do whatever, otherwise the pointer stays in one place. Does anyone know how to sort this out?
I know this seems stupid, but I cannot find a solution.
If you can help, please post. Thank you!

Does this happen with other games?

I’m not sure. It worked fine on the old computer, but this one is brand new and has all the recommended requirements for the game. To be honest, I don’t play Counter Strike.

You should try testing it, just to check if the problem is only occurring with gmod

Alright, thanks.
But if it doesn’t work, have you any idea what I should do?

EDIT: Counterstrike won’t let me aim while walking either.

Check keyboard and mouse settings.

Which ones? In the options?