It could be a number of things. Too many programs running, excessive temporary files, spyware, malware, virus. Could be Windows updates, fast start up needs to be unchecked or a defrag is needed. Write down more details of your hardware profiles like psu, SSd or HDD, running new programs or updates. Keep in mind if you're running newer more resource using games the 970 slows down when it's taxed for all 4gb.
With the little information you've given, the first thing I'd do is a speed test of your internet. see if the problem's isn't something outside your system. Then run a virus scan, go to C: drive and run the Disk clean up in C: Properties, then in the tools tab run the Error Checker ('Check now') and Defragment tool. Spyware scan...