Frustrating problem with my inspiron 5547

Hello, Thanks in advance for anyone that decides to help. I'm not too sure where to post this but this seems like the right place.

I bought my inspiron 5547 back in around 2015 and it has worked perfectly ever since. However, until around a year ago, I noticed that games started to have significant fps drops. I thought it was no big deal so I continued to play normally. However as I started to play fps games that ran perfectly well before, I noticed that they were virtually unplayable. There would be a few minutes where the games run flawlessly, but then I'm hit with a sudden random fps drop for a few minutes before it goes back to normal and the cycle starts again. Runs well, huge fps drop, runs well, fps drop. It was no big deal before but now it makes literally any accuracy based game unplayable. The most astounding thing about this is that the laptop can run all of these games perfectly well. I was honestly shocked to see that a visual novel (Literally just a set of pictures) even had an fps drop. Its strange that it only affects games. I would really like to fix this issue since I tried everything. I even reset the entire laptop but nothing worked. I just bought some games during a steam sale only to find out that the only one that I can play without any fps drops is Half life 1. I only play old games so it's really shocking to see these drops on 10+ year old games. I would appreciate any help possible. 

These are my specs:

System Model Inspiron 5547

Processor Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz, 2401 Mhz, 2 Core(s), 4 Logical Processor(s)

Installed Physical Memory (RAM) 8.00 GB

System Type x64-based PC