16GB of memory

RAM is not the problem.. what model?

One factor is the form factor, the smaller the notebook is the harder to cool it is. And smaller fans means higher RPM (louder) and longer runtimes.
Also Dell sells some "business" models which are underpowered even for medium sized Office loads e.g. in Excel.

Is it new? Then it maybe Windows still optimizing itself..

It's a e5450/i5 5300U @2.30GHz running a 64bit Version of W10 (1903) it is not new -nearing end of warranty but a new board was just installed.

is your task manager/performance cpu  very low..

It doesn't matter how many apps are running it depends upon what the apps are doing..  i.e you only are running prime 95 then your cpu will be maxxed out and your fan will be running full speed.

check that the vents are not obstructed.

There is often a setting in the BIOS about whether the fan should be temperature controlled or not.  I've seen one Dell tower where the setting was correct (speed control enabled) but the case fan ran at full speed (rather loudly) all of the time.  I flipped the BIOS setting numerous times with no change.  What finally fixed it was to reset the BIOS to defaults.

If you do the reset to default, make sure to note your settings (especially those related to Secure Boot and SATA) beforehand and put the old settings back when done.

Is this a laptop or a desktop?

In addition to checking Dust build up (poor air flow) as suggested by  David Johnson:

Malware, Viruses, Update downloads/processing and drive issues can also tank your CPU and sometimes memory usage causing fans to take off: Especially in a laptop as they tend to run hotter due to size and limited air flow