R Studio creates small plots images

New to R studio here.

Lately something went wrong with R studio.
Everytime I create a plot (that can be a corrplot, a histogram etc) it shows as a little image, roughly 1/4 of how it used to be. It has not anything to do with the panel's dimension or with maximizing the plot window.
Below I provide an example:

The plot is smaller than the whole image and it is located in the upper left corner of the image instead of being at the center. Open the image in a new window to understand.

How do I fix this ?

Because you say "everytime I create a plot" it could be that graphic parameters were set in your .Rprofile .
See e.g.

op <- par(mfrow = c(2, 2))
plot(1:4,1:4)


Created on 2021-09-12 by the reprex package (v2.0.0)

results in (I made a screenprint of the Viewer panel) :

Yeah, I agree with you. Do you know how I can reset those values in .Rprofile ?

The .Rprofilefile is just a textfile with R commands.
So if the file contains the graphical parameters then just erase these lines.
The only problem is to locate the file(s). See e.g. https://rstats.wtf/r-startup.html#rprofile