Disable overclocking?

Hello, I currently own and use a stock-ish (I have upgraded the RAM memory) inspiron 5680. I noticed recently when I looked at my task manager that my CPU was running at near 3.8 GHz. However the base speed for the    i5-8400 seems to be 2.81 GHz, or so the computer claims. Is there a way I can prevent this overclocking? Or is the claim of a base speed of 2.81 GHz a false claim and I should ignore it? The computer runs fine as it is, I am just interested in how do disable this.

 Yes I know I need to restart my computer more often. I have had corrupt memory issues with this computer before and had to reset it multiple times. It got corrupted to the point where I could not reset the system in any way on the system itself, I had to install windows from a flash drive. This is for another post though.