If Premiere Pro 2018 is not working...
If you are experiencing a huge difference between the 2017 and the 2018 version of Premiere Pro, there are a few fixes that go beyond the simple delete cash files and delete preferences.
One little thing is to reserve the maximum amount of RAM to Premiere Pro. There is need for your computer to calculate faster and RAM will definitely help, but by default the memory is spread out with all your software and this is an easy fix!
First thing that can definitely speed up the process is to have 3 separate HDD (or better SSD) to serve Premiere. It's not too costly, but the results will literally blow your mind. The setup is extremely simple:
Have the main hard drive (C:)—where all software is installed—free from any working file or clips. It's always better to "leave alone" the hard drive that is holding your main software, this will speed up the opening of the software, update faster, etc etc...
Have a dedicated hard drive exclusively for the clips and for the working files of Premiere. When opening a complex project there is a lot of reading to do and having these files on the same HDD that other software are running is not a good idea.
Have another hard drive that will host only the media cash files. We all know that Premiere needs not only to read video files but to create peak files and media cash files per each clip and these files will be read each time we open the project. For this reason your bottleneck might be having all on one hard drive that needs to deliver too much information while working on the main OS and other software that you might have open at the same time. You don't have to delete the files—even though it will save you a few Gb of space on your C: drive, but when changing the folder you have an option to move the cashed files, which is faster. If your projects are not too complex I recommend deleting and making Premiere Pro generate new files in the new location...but this is up to you!
By default the file is hidden in the common resources of Premiere, but you can choose a different folder and obviously a different hard drive. Separating these operations will speed up incredibly your workflow and your exporting process as well because each of these operations that are extremely heavy will be separated on each hard drive.
If you have more $$$ you can have three RAID0 or (strip) to boost exponentially the read/write speed, always keeping in mind to have 3 separate locations to have clips/working files, cash and software.
Hope this helps and if it doesn't I recommend installing 2017 till the 2018 gets a few bugs fixed.