Loose back screws could contribute to rebooting.
I was just checking my screws on my Z10 (was bored), I have the tools so I decided to make sure they were tight. I remember my bold 9000 had loose screws in 2008 and it would restart randomly anytime you gave it a jolt or put it on a desk. Six of my screws on the Z10 were loose slightly.
Just thought I'd mention this because it could contribute to random restarting. If the middle piece and back piece aren't tight the current can be interrupted and restart or shut down the phone. Another possibility is a loose connection inside the phone or even a lose battery that interrupts current flow once the device is placed down on a table or in a pocket, any type of shock would cause a restart.
Don't do this if you don't have the tools, it's easy to strip the screws and you might cause damage and void warranty.
Just a FYI incase someone else finds their screws loose. I think I used a t5 screw driver.
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