Reaching 90c is a real problem, especially if that happens in less than 5min. Think about the temp it will reach if it didn't crash and you were gaming continuously for more than 30min, it would've gone over 100c which can damage the CPU. So the crashing seems like a protection from damaging the CPU.
The case isn't getting hot or the exhaust from the fan? That could mean a bad air flow inside the laptop.