Unfortunately, it's quite difficult to get to the bottom of issues such as this -- not all users are encountering this issue, so it may be some sort of bad interaction between RStudio and your environment, or the way your machine / R is configured.
We did have some reports from Windows users related to slowness when using View(), as discussed here:
You didn't say what version of RStudio you're using, but if you're running into the same issue, it should be resolved in the latest release (v1.1.442).
If you are still having issues, a diagnostic report may be helpful.