OK. In short, here is a way to troubleshoot with limited tools.
Discount everything that is not needed to get the PC boot up.
Use whatever diagnostics or in the firmware (BIOS) of the motherboard. If there is an intensive memory test, do it. Maybe an hoer or more.
If you do not have a spare Hard Drive, now is time to buy borrow or beg for a hard drive to be used for a new install of Windows 10. But this time without the SSD. Even a small HDD will do the job for testing. Even a 20 GB will do the job.
On eBay a 40 GB from a major maker goes for about $20. This should be part of your tool box, as drive problems are still among the leading source of PC problems. Even when a drive will pass a test, it can make trouble later. So a spare drive is an important tool for testing. And has the benefit of not messing with your data if something goes wrong.
Hope this is of some help.