Restarts never are. Resets are. You need reset all SFRs to their power up values and - at least everytime I tried - you will forget one or two (OH that one is not used, no need to bloat the code initializing that).

The WAY to restart is to use a watchdog and let it time out that gives you a reset. If you use a chip with an internal watchdog and do not use it, just use it for this purpose. You will, by using a puppy avoid much pain.

Erik