my laptop sometime "restarts" when i lock it. basically sometimes when i will leave my room even just for a couple of minutes i will lock it using "acer power button" then when i came back i'll just input my password again then i'm back to normal. but sometimes my laptop seems to restart after locking. example i will lock my laptop and go to the nearby store, after i came back i'll input my password it will load then it will start the start up applications which i already closed and my open application are all closed. in short my laptop kinda restarts even i only lock it. it's not that big of a problem but 1 out of 10 of "lock" will have a "restart"-like after inputting password. any clue as to why it happens and solutions guys?