Note that Fedore 25 has switched to a new graphics called Wayland. Some existing software may not function properly until it is updated to work with Wayland. Check this forum, and you will see that you can start your sessions with a variety of graphic options. You might want to try these options first, since your problem may be related to the new graphics.
You may also be interested in the following troubleshooting procedure, but you will need to back up all your data and note your configuration, because you would do a clean reinstall of Fedora 25 using the ISO image burned on a DVD or Flash Drive. If you can't afford to do this, I understand. In that case, please disregard my advice and hopefully someone else can help you.
IMPORTANT: Please read carefully and proceed at your own risk. Please back up all your data before trying this procedure. ALSO IMPORTANT, if you use windows, create and update any recover media that comes with your windows version. Any time you reinstall an operating system, you risk losing everything on your main hard drive (the one you install the OS and boot on).
reinstall Fedora 25, overwriting your existing Fedora installation. If you dual-boot windows, you can probably overwrite Fedora without disturbing windows. NOTE that some people have had issues dual-booting windows and Fedora 25, but people on this forum have been helping them overcome their problems.
Once Fedora 25 is installed, update your system BUT DO NOT INSTALL ANY ADDITIONAL SOFTWARE. If you normally use Firefox sync, don't enable it just yet, since it will automatically install add-ons. You don't want to install any new add-ons or plugins just yet. If you use Chrome or Chromium, just wait and use Firefox instead. We want to test with only the stock distribution and available updates. Note that it is OK to configure your system within reason. Just make sure to avoid installing additional software or plugins. Also, use the default graphics (Wayland) initially for your tests.
Use your updated stock distribution for several days, and try to get it to reproduce your problem. Don't install any 3rd party software yet. You want to find out if the problem is with Fedora 25 or with the software that you choose to add later.
4.a. If you still encounter your problem with the stock Fedora 25 distribution, try switching your graphics option to see if the problem is solved. If so, the problem is possibly a 3rd party issue. If not, the problem may be with Fedora 25. Either way, please file a bug report. If you don't know how, someone on this forum can probably help you get started. I've never had to do it (yet), but the people on this board are intelligent and helpful.
4.b. If you don't encounter your problem, then make a prioritized, grouped list of the software you need to install to actually use your ... (more)
Were you using Chrome, Chromium or some other browser? The reason I ask is that I just came from Ubuntu 14 LTS, and I had a lot of trouble with both of those browsers crashing and locking-up the GUI. Note that Ubuntu 14 LTS uses Unity and Mir, while Fedora 25 uses Gnome3 and Wayland. It's a long shot, but I thought I'd ask.
NOTE: I also ran into trouble with Firefox crashing on Ubuntu 14 LTS, but I traced that problem to add-ons I was using. Could you have added (or started using) an add-on recently? Call me crazy, but I always suspect 3rd-party software first.
I'm using Chromium, but I never had problem with it on Fedora 24.