My Mac keeps shutting down for no reason

Impossible to answer with information provided.

We have no way of see your Mac so you are going to have to tell us

exactly what model of MacBook Pro you have

disk space

amount of RAM

what operating system are you running

any error message you might be seeing

Allan

I have been having the exact same problem as of today. Macbook 5.2 running Leopard 10.6.8.

The 'Are you sure you want to shut your computer down now' window appears sometimes... It appears to have formed a connection to the CD/DVD eject key. Pressing this key brings up the Restart-Cancel-Sleep-Shutdown option. 15 times whilst TRYING to type this.

Reset the SMC, which can sometimes fix shutdown issues. See this Apple note: http://support.apple.com/kb/HT3964

I have the same problem, 15inch Macbook Pro from 2010

I have a new Solid State drive 256 gigs 55gigs avaliable left

Sometimes it restarts for no reason, at first I thought I was hitting some restart button combo, but then noticed it would restart even when I'm not typing.

So trying out that SMC reset, hoping this fixes the problem.