There are multiple problems here.
That motherboard has trouble with FX CPUs above the FX 6300. It's simply not built for these power hungry 8xxx series CPUs. Try the M5A99FX PRO R2.0, that's what I used to get to 5.2GHz on my 8350.
Also, the FX 8350 thermal throttles at 55C, so that seems about right.
An overheating issue coupled with a weak power delivery system will produce a rather unstable system. You need to replace a few components, mainly the motherboard and CPU cooler.