Why does my laptop freeze when i lift it?

I have a gateway laptop MN: W323-UL1 M: MX3230 and every time i lift it to go somewhere else with it, it freezes..so, i have to turn it off and back on but sometimes nothing shows up on the screen, it's just black. i've checked the ram, the hard drive and i've just recently put some more thermal grease on the intel. but it still freezes...sometimes i will lift it barely and it does it. but for some reason when i tighten the screws on the heatsink it. will work just fine. oh! and it only freezes when i lift it on the left side. i hope all that makes sense.