You need to help us first ...
OS, CPU, RAM, GPU, vRAM ... and also disc layout & connections can be useful (as in, "2 internal hard-drives and an external on Thunderbolt connection for exports")
Specific build of Premier Pro from the bottom of the "About" splash screen off the "Help" menu is best.
Footage file type: MXF, AVCHD, MOV, m2s, what?
Even the camera it was shot on can be of interest at times.
And did you use media browser to import, then project panel to drag & drop?