I have an Acer Aspire V5-471 and I operate it without a battery (screen doesn't get power due to an unknown reason when it's mounted). When I first boot the laptop, it starts normally. But when I put my hands on it (any weight that applies) it shuts down suddenly without prior alert. Two or three consecutive times it happens, then it starts up normally and doesn't shut down. It happens whenever it is opened after a long break (3+ hours).
Is the laptop going to work without any issues, if you do not apply pressure on it? If yes, then it really seems that there may be connectivity or motherboard issue. Do you think that the laptop may be overheating? Check that and run test on hardware like RAM memory and hard drive. What happens if you enter BIOS and navigate through its menus? Does the laptop shut down?