Windows 10 Computer, Performance drops dramatically after battery dies

Question

My apologies in advance for asking another "my computer is running slow" question. I'm not sure that there is anything unusual about my situation but I'll post the details and let you all decide:

• The machine is a Yoga 2 Pro with 8GB RAM and a SSD. Considering I bought it in early 2014 I'm surprised with how well it runs.
• While on the move yesterday I was using the laptop at a hotel. It operated fine. I closed the lid to put it into sleep mode and took it to the gym where it sat in a backpack, and then walked home with it after.
• That night I saw that the battery had drained and it shut down (while the computer always ran at a good speed, the battery barely lasts 1.5 hours anymore). I plugged it in and turned it on. At this point I noticed it was incredibly slow.
• I tried rebooting the machine but the problem persisted. The CPU is around 9%, RAM is around the 40-60% range, and disk usage is currently at 1%.
• To give you an idea of the performance, if I load a webpage it takes an absurd amount of time to render, almost a minute. In general, I can type faster thatn the words can appear in many apps, particularly Cortana. Pressing the start key I might have to wait around 8 seconds for something to appear. Even then, once the menu comes up, I would wait another 3-4 seconds for the icons that represent the programs to show up. Pressing the start menu again, however, will bring it up much more quickly leading me to wonder if it is a hard drive issue.
• I tried running "Optimize Drives" to check for fragmentation, but the Analyze feature of this program is disabled for reasons I don't understand.
• Malware bytes and Windows Defender both show that there are no threats.

Because this problem happened instantly, rather than gradually, I'm not sure how I should proceed. Configuration issue? Factory reset? Buy a new machine? Any input is welcome.

Answer 1

The problem is fixed, and I will outline the steps I took on the way to performance returning to normal, but what I am not certain about how helpful this will be to other people.

I contacted a company that works in this sort of thing and they remotely connected to my PC and grabbed the process logs to analyze my system. They said their technicians pinpointed the error and it was definitely software related. They stated they could fix it for $200 (but would not tell me what the exact error was until I paid, obviously).

I didn't want to spend that kind of money so decided to try a few things on my own. The first thing I did was to close processes and shut down services 1-by-1 to see if I could pinpoint the culprit. This yielded no beneficial result. I then decided to reboot in safe mode before deciding on doing a factory reset.

The first time I rebooted I wasn't able to successfully get into safe mode. I was about to try again when I noticed that, lo and behold, everything was running normally! Obviously this is weird: there's not really a good reason why stopping services and killing processes would have an effect since they would all restart on reboot. So I can't really advise this as a course of action for anyone other than the truly desperate.