For hardware checkout is best to download "Apple Service Diagnostic DVD" ( ASD ) for Mac Mini G4 and make tests with it. It is free somewhere on apple and other websites.
other what can you do:
- replace thermal paste between CPU and coller, check if cooler proper fixed.
- check real CPU temperatures with MacOS or MorphOS tools
- check if you have latest firmware
AmigaOS3: Amiga 1200
AmigaOS4: Micro A1-C, AmigaOne XE, Pegasos II, Sam440ep, Sam440ep-flex, AmigaOneX1000
MorphOS: Efika 5200b, Pegasos I, Pegasos II, Powerbook G4, Mac Mini, iMac G5, Powermac G5 Quad
