Latching relay question

Do latched relays in general "wiggle" back and forth (if even for a 
fraction of a second), or do they work as a firm and precise on/off
switch?

I'm planning to cut/supply power to an external SATA hard drive by 
having the +12V and +5V lines through a relay (dual pole), controlled by 
a momentary push-button. But if the relay "wiggles" from one position to 
another when activated I'm worried that this will in the long run harm 
the drive (from what I've been told it's harmful to most electronic 
devices if you switch it on-off-on-off... quickly), so like a mechanical 
switch I want it to be in either a definite on or off position when I 
activate it.