Study the data sheet as to initial values in the SFR's, typically you must restore a lot of those in a soft restart. Do not overlook that whatever you need to do, the FIRST thing is to disable interrupts. In the only case where I ended up doing it soft I started in the startup code with setting what was already there on a coldboot and then made my warmboot simply jump to 0. The softboot is a hornets nest, every change of the code will lead to - forgotten - additions to the softboot. The real problem with softboots is that often a faulty softboot will work 99 times out of a 100. GET A WATCHDOG and trigger it.
Whatever you do, have fun
Erik