One possible reason, for the issue you are seeing, is that one or more of the apps or processes during startup is causing a significant amount of CPU processing. Thus raising the temperature and running your notebook's fans at full speed.
I suggest that you start by taking a look at any startup items that you, or an app, has configured on your notebook. To simply do so, go to System Preferences > Users & Groups > Select your user account > Login Items tab
The image below is from my 2010 MacBook Pro, which does run a number of things at startup. I would expect that you will get very different results.

To temporarily disable any that you have, hold down the shift key after you enter your user account password, but before pressing the return key. If this resolves the issue, then you know that it could be one of these items that may be causing the problem.