I doubt that someone will be able to exactly point at the root of your problems. You need to perform some tests and essentially simplify your PC configuration step-by-step until the problem disappears.
1. Hardware
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Slightly de-overclock your CPU, RAM and GPU, say, for 5% frequency. Alternatively, if your BIOS allows to have several user profiles, switch to a normal profile (for test, of course). This will completely exclude a chance of overclocking-related problems.
Check the conditions of your CPU and graphic board, their fans, also remove dust. This will exclude the possible overheating.
Check your HDD, delete junk files. Check the free space and fragmentation level (non needed for SSD). Use the appropriate utilities, like CCleaner and Defraggler. This will exclude the possible delays due to heavy fragmentation, incl. paging file.
2. Software
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Check the resident programs loaded at start-up (Task Manager, Msconfig, CCleaner). Temporary disable all unnecessary programs and utilities in start-up, including those you use for work or gaming (they can be launched manually when need). Check whether the problem still exists with minimal amount of residents.
Check the situation with anti-malware program, for example, Windows Defender. For test, disable the real-time protection (don't forget to enable it back later). Another possible source are the automatic scans, which may happen too often (noticed with recent WD updates) and consume the lion's share of CPU resources. Disable such scans, e.g. for Windows Defender: Task Scheduler -> Library -> Windows -> Windows Defender -> Windows Defender Scheduled Scan: Disabled.
Check which hardware drivers have been recently updated, because they may be a source of problem too. If you suspect a particular driver (sound, video etc), uninstall it and return to a previous version.
The same can be done with software updates. In particular, check your Discord version and try to install a previous one.
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If nothing above helps, use System Restore to return to a date when the problems didn't happen. Use this carefully, as a last resort; even if this solves the problems, it will not point at the particular reason. You will need to do more tests.
