Performance problems - Very slow and studdering

What about disks? Hard drive or SSD?

You see, the combination of the relatively weak CPU and your storage system plays a HUGE role in this stuttering performance. Your CPU, despite being branded i7, is only a dual-core CPU with hyperthreading (only 4 threads total). And in my testing no dual-core CPU, even with hyperthreading, is as powerful as even a mediocre true quad-core CPU, let alone the 6-core or higher core count CPUs that we generally recommend.

And don't rely on the number of CPUs in the Windows Task Manager: They just show the total number of processing threads. However, the total CPU usage and the disk throughput usage will tell you something: If one or both of those are either maxed out or are close to being maxed out (while at the same time the memory usage is on the high side), then your system's hardware configuration simply isn't powerful enough to handle this video content while running Premiere Pro.