|I like all of the above.|
Seriously, If restarting the machine does not fix it, you may need to open it up and look for that loose connection. If that does not do it, you may need to reseat connectors and memory modules, and possible test some of your hardware.
For the long term, move the machine off the table and put it on the floor, elevated above the floor (better), or on a vibration dampening mat on the floor (better) (assuming you are not into kicking or punting).
Added: assuming a 'desktop', not a laptop...
You have to be a little bit crazy to keep you from going insane.