Every time I open Sims 4, I get this message: "Your computer has insufficient memory to run The Sims 4 with your currently installed pack(s). This may lead to poor game stability."
The game seems to run fine except sometimes it lags a little, the sims stand there doing nothing, and actions aren't completed
You get the warning because you only have 4GB RAM which by itself is enough. However you only have integrated graphics which means that it will use some of that RAM.
Adding additional RAM will help. Consult your manual to see if it is possible and what type you will need. Notice that you may be unable to run any of the two latest Expansions with the current setup because they have higher minimum requirements.