I do wonder what area is heating up too much.. I agree, it does seem to be that as I push mine a little ... and I mean literally a few chrome/FF tabs, outlook and then open Excel, it will kick in.
BUT
if it was heat, why are the fans not going nuts? in fact most of the time mine are very slow spinning when it starts shaking,
Anyway I've had speedfan running the past hour or so and again what it reports back does not tally up with temperature ups and downs.
For instance:
Idle = I'm browsing with my cursor, stop for a few seconds and it shakes until I move cursor (or just leave task manager running on the side)
Shaky = Shaking while I'm using trackpad/keyboard/working away and nothing is stopping it including task manager running
Very shaky = this is as shaky but as good as unusable as it's too much shaking (here the fans do go slightly higher but not full or even nearly full).
*All temperatures below are in degrees celcius
Idle Temperatures:
HD 0: 38
Temp1: 47
Temp2: 0
Temp3: 37
Temp4: 40
Core 0: 33
Core 1: 26
Shaky Temperature:
HD 0: 41
Temp1: 48
Temp2: 0
Temp3: 40
Temp4: 43
Core 0: 31
Core 1: 28
Very Shaky Temperature:
HD 0: 40
Temp1: 52
Temp2: 0
Temp3: 39
Temp4: 44
Core 0: 45
Core 1:44
When it stopped shaking altogether:
HD 0: 39
Temp1: 46
Temp2: 0
Temp3: 39
Temp4: 42
Core 0: 31
Core 1:31
When it start shaking (shaky not very shaky)
HD 0: 39
Temp1: 51
Temp2: 0
Temp3: 38
Temp4: 43
Core 0: 39
Core 1:36
As you can see, it's not obvious.
It's not HD0 temp as it was shaky @ 41, stopped @ 39 and shaky again @ 38
It's not Temp1 as it 48/51/52 when shaking but 61 when it stopped
It's not Temp2 as these are not monitored (so maybe it is who knows)
It's not Temp3 as these are very close and stopped @ 39 but shaky @37/38
It's not Temp4 as it stopped @ 42 but was shaking @ 40
It's not Core1 as it was shaky at 28 but stopped @ 31 yet started at 26
The only close one is Core0 which in every result of shake was equal or higher to when it stopped but it's so close... who knows
Anyway it's not my job to analyse and diagnose a product that is clearly faulty across thousands of people so I'll leave it at that.