I bought a tablet a few weeks ago was constantly shutting down

I bought an Acer Iconia one 10 returned it within a week as it was shutting down and the screen would freeze, I got another, however this one is also shutting down the screen goes black it is brand new so it doesn’t have many apps on it except what it came with..... I’m not sure why it is so slow and shutting down when it is brand new.....thinking I am going to return this one as well and get another brand as this is the second one In three weeks with the same problem.....wanted to check to see if there is a setting or a button I’m hitting that’s causing the black screen or is there a problem with this particular tablet...thanks