Have you tried to fix the problem in anyway just yet?
Disclaimer: I am in no way shape or form a computer wizard and these are all suggestions and should not be taken a legitimate technical support advice (even I crash sometimes).
1. First thing I'd try is to validate your game files. You can do this by going to your Steam Library -> Garry's Mod -> Properties -> Local Files -> Verify Integrity of Game Files.
*Reducing the amount of addons you have may also help performance + also make sure everything needed for the server such as the content pack is downloaded.
*Make sure your drivers are up to date.
2. The second option would be to do a complete uninstall of Garry's Mod on your computer. To do this I would recommend going to your Steam Library, uninstalling Garry's Mod and then going into your garry's mod steam folder such as "steam/steamapps/common" and deleting the actual Garry's mod file. Clear your recycle bin, restart your computer and ensure that both game and the files are gone, begin reinstalling and see if the issue is resolved.
3. If it's a memory issue, some articles online may be able to help you. Otherwise you may be on an outdated Hardware DirectX level, I had tried to change my level from v9.0 to v8.1 to try to reduce lag, but encountered crashing due to lack of "memory." With fixing my level back to my software DirectX level I had stopped the memory crashing issue. (This memory issue was specific to me, it may not apply to you.)
4. Reducing your settings/ graphics may help with FPS if that's the cause of the crashing.
5. If it's a computer issue and you've already tried other potential fixes like cleaning your pc, uninstalling programs you may not need, etc. you may refer to the information below.
If you have backups on your computer and remember a point in time when the issue did not occur whilst running Gmod, you can try to reload that backup.
As mentioned in the post above, a final potential fix may be to perform what is known as a factory reset, this should reset your computer to a factory new position with minimal to no applications downloaded, etc. (Starting off fresh) If after the factory reset you continue to have these problems I'd say it's a hardware issue. I'm not sure if you would need the disk that sometimes comes with PC's when you buy them for the factory reset, but I suggest being prepared and using the reset as a last resort.
I hope any of this helps you and continue your fun experience on the server!