factory reset and now my computer is running so slow

I suspect the SSD is failing if all you had to do to "fix" the system was run First Aid even though it did not actually repair anything. Run DriveDx so we can check the health of the SSD and post the complete text report here using the "Additional Text" icon which looks like a piece of paper. Unfortunately the Apple SSDs don't provide much health information, but it never hurts to check. Plus most SSD failures are due to the SSD controller which doesn't really have any health information.

The best way to confirm an SSD failure which is intermittent, is by installing macOS to an external USB drive. While booted from the USB drive, you can try sleeping & waking the laptop multiple times (you may need to let the laptop sleep for a little while). I find a lot of SSDs fail as they "wake up" since they may be a bit lazy & take too long to go ready. If the internal volume disappears when waking the laptop, you need to confirm whether the internal SSD's hardware is still seen by macOS. You can do this in three ways:

• Check Disk Utility....you may first need to click "View" within Disk Utility and select "Show All Devices" before the physical SSD appears on the left pane of Disk Utility. The physical SSD will be identified by its make & model such as something like "Apple SSD...."
• Check the Apple System Profiler (Option-click the Apple menu & select the first option). If this is an Apple original SSD, then click the "SATA" item on the left pane to see if any hardware information on the right pane. If it is a third party NVMe SSD, then click "NVMExpress" instead.
• Use the following command in the Terminal app to see if the internal physical drive is seen:

  diskutil  list  internal

If the SSD is no longer seen, then you have confirmed a hardware issue and most likely a failing SSD as the SSD is the weakest link here. I suggest you use at least one of the above three options before performing the sleep & wake test so you know what should be shown when the internal SSD is working. Unfortunately you cannot perform this test while booted to the internal SSD.

If you are using a third party internal SSD, then perhaps the SSD adapter is bad or incompatible.

You can also try running the Apple Diagnostics, but the diagnostics are unlikely to see any problem with the SSD when the failure is intermittent.