Welcome to the Forum....
There can be 2 reason, 1st its because Software problem, 2nd Because Hardware problem...
If software, make sure your PC is not infected with Virus or Malware, use AntiVirus Softwares, good AVS like,
nod32 or
Kaspersky
now after installing any of them, and after running a full system scan, if you find system is virus free, then Sorry Sir, it would only mean problem is with the Hardware, so only way out is Taking it to Acer Support !!! as they would be able to change the faulty part with a new one