I've had my N9 for about a year now, replacing a N900 (miss the keyboard). While I still keep it since there is nothing out there that even approaches the overall experience, even without the hardware keyboard, my particular unit is starting to become hard to use.
I had some random reboots from day 1 and they got a bit better after the successive updates (e.g. Drive is no longer rebooting the phone all the time), but I still have some reboots usually when I try to start a call or when I try to answer a call. At the moment I press the button there is a reboot. Very annoying. Oh, and once it was when the alarm started.
What's more, for the last few months, I've had the messages app show "no messages", unless I wait for over 20 secs and then my SMSs start to appear. This started a little before the last OS update and the update did not fix it. More recently, I have started to experience slowness in recognizing a phone number that is in my contacts list. Most of the time, even if I let it ring for a while, the phone number is not translated to a name from my Contacts. if I wait more (usually after I have answered) at some point it finally resolves and shows the name instead.
I could stand the reboots, with my usage (not too many calls) they would occur once or twice a week, and since I am in Greece where the N9 never officially came (mine is from Denmark, 64GB black), I am not sure how easy (or slow) it would be to have it serviced so I just waited hoping it was a matter of another update.
But the other issues have made my wonderful phone hard to use. I am attaching a log that ends after my most recent reboot in case someone can help out. I can't see something significant at the moment of the reboot, although there are a lot of Fenix debug messages and also some troubling i2c_write: Remote I/O error.
So, anyone very familiar with the N9 can spare a few minutes to take a look? Thanks!

PS. Last time I opened a N9 syslog it was just 1kb, I wonder how I got such a big one now.

Just a wild guess, but you mention that Drive *and* using the telephone caused reboots, and your syslog has errors related to csd (modem) saying "Internal modem communication error" *and* nped (location services) saying I/O error when reading from the i2c bus (gps, I bet).

So, again this is a wild guess, your modem chip (which I bet contains the GPS as well) is either broken or has a loose contact (reminds me of the famous "All telephony functions disabled" on the N900).

If that's the case, you need to get the N9 repaired.

I would anyway try a reflash first!

Holy crap that's a buggy experience.

Have you reflashed? If the problem persists, your Black 64GB N9 may have a faulty eMMC (this was an actual problem when they first came out quite some time ago, disappointing a large portion of TMOers)

Note that the ones with buggered eMMCs mostly come from Finland.

Just to add, though I haven't read you log, for the messages issue I am pretty sure you have more than 2,000 messages...

If you plug in your phone to Nokia Suite and have >2,000 messages it will tell you to allow it to store the messages on your PC and delete from the N9 so that your phone doesn't slow down...


Edit:

I've started looking into your log and have started from the bottom and saw the following:

This means your tracker is beginning to screw up...You may want to check /home/user/.config/user-dirs.dirs to see if its in proper condition...


Edit 2:

Can someone help on this line:

Does it mean anything significant? I think the OP has done OTA updates till pr1.3 hence should do a clean full flash...

Thanks for the replies. I will try reflashing to see if that fixes anything. When you guys say reflash, do you mean using the Nokia Software Updater to re-install the latest OS? I assume that is the safest way, right?

I don't have that many SMS messages, but I do have that many email messages. Does the latter affect SMS as well?

Email database doesn't affect the messaging app AFAIK...

For doing a clean full flash you may want to refer to this...

Please backup all your important stuff including apps, messages etc using N9QTweak first before attempting a flash...


Edit: Email messages are stored in userfs partition so if you have a huge number of them maybe you want to post from Settings->Device->Data Storage the available space in all the 3 partitions...

Doesn't seem to be a problem there:
Installed apps 2.3/4.2GB
App data 521.7/2.1GB
User data 10.8/57.7GB

I think you should the attempt a full flash of rootfs+emmc...

Jut make sure your data and stuff is backed up beforehand to your PC...