Windows 7 Very strange problem- need help

Hello everyone,
I have a Sony VIAO running windows 7. The laptop is about 3 years old I believe. I'm having an extremely strange problem that seems to have no solution. About a year ago, one day out of the blue, the laptop went crazy. I would try to type something and whenever I pressed a key, it would pull up random programs and send commands and type multiple letters at once. Then the screen would get all laggy and the fan would come on full blast. It was completely unusable. I tried restoring the system and resetting a few other settings (don't really remember what all I did a year ago) and nothing seemed to work. Then one day, once again out of the blue, it was completely normal. And it stayed normal for a year, up until a few days ago. It's now doing the same thing. Does anyone have any idea what's going on? Every so often when I start it up I'll get a black screen that says "operating system not found" and I have to pull the battery. When I turn it back on, it's fine. Is it possible that reinstalling windows would fix this issue??? I'm so lost.
Without having a whole lot to go on, this sounds to me, a bit like a hardware issue that might be indicating a bad connection or multiple bad connections which could be a result of the laptop having been dropped or otherwise mishandled.
And the mere handling of the laptop, turning it over to remove the battery, may be providing the extra bit that the connection needs to re-establish itself.
Depending on how handy you are with respect to mechanical things, the first thing you might try is examining the ribbon connection to the keyboard and trackpad. I would also take a look at the hard drive interface connection and confirm that it is firmly seated in place.
Then I would definitely run the native Check Disk utility to see what might be reported with respect to any corruption or bad sectors.
Admin command prompt and type
chkdsk C: /R
hit enter
answer Y when prompted and reboot.
Let it finish and inspect the results in Event Viewer.
Thanks for the reply! I bought the laptop used in 2011, I suppose the person before me could've mishandled it and I would have no idea. It's just strange to me that the problem would go away for an entire year and then reappear exactly as it did before. As much as I HATE to admit it, it did fall from my desk a few months ago. I was so scared to pick it up after but it appeared fine. No problems directly after. So again, why would the problem only present itself months later?
As I said above, a loose connection might manifest itself in any number of ways and turning the laptop on its' end or back or upside down or whatever may cause the connection to fail or cause the connection to succeed.
Another thing to consider is relative temperature. Hot = expand, Cold = contract.... sometimes that is enough to complete an otherwise open connection.
Again, these are just guesses but a place to start.
Yeah I appreciate the opinion and definitely get why you would suggest that. I too thought that it was some sort of internal problem but with very little knowledge of computers, I could never say exactly what the problem was. So you think if a loose connection is the case, that It would be an easy fix for a pro?
Pro(s) come in various shapes and sizes, but I would suspect that someone or some business who does laptop service and repair might be able to do some quick trouble shooting for you for a nominal fee, usually a diagnostic repair which can then often be rolled into any additional service charge if you decide to move forward with repairs.
Often checking the keyboard and trackpad ribbon cables and removing and reinstalling the hard drive doesn't require a great deal of skill and you may even be able to find some instructions or videos on line that may help you if you decided to give it a go yourself.