Task manager can tell you how hard it is being worked by whatever it doing.
HW monitor from CPUID will tell you what internal temperature the CPU is running at
https://www.cpuid.com/softwares/hwmonitor.html
Taking the two together a laptop CPU working hard can end up running at 80c 'normally' although 60c or 70c would be nicer for it.
CPU's usually reduce their work rate to try and avoid passing 90c and generally this systems avoids protective shutdowns at 95c +
If there is little workload from you but it's reaching 70 or 80 c the CPU heatsink or cooling system/fan is suspect
If the CPU is on 100% with little activity from you there's a virus/trojan or internal software conflict (Windows updater problem, 2 virus checkers colliding etc) going on
If neither is happening mechanical or electrical problems are your main suspects - if you find it runs fine upside down for example bad connection or soldering is very likely