I have a nokia n9. Often restarts. What could be due to the frequentrestarts? The phone is new. Since the operator Orange Poland.
Network intervention is usually bad news. That's why I avoid them like a plague. My vanilla version is very stable and no problems so far. Touch wood.
However, restarts are commonly associated with faulty sims so worth a try.
On a different SIM card is the same. Is the Nokia Care can downloada clean soft? Or is it a defective copy? The phone is under warranty,so I have to use it. Thanks for your interest.
You should perhaps consider resetting your phone first. Backup your data, then goto Settings>Reset>Clear device. This will wipe the phone and return it to the out of the box state so remember to backup essential data first.