Nexus 4 switches itself off

I own a Google Nexus 4, which is a great Android phone for the price, but recently I have had problems with the phone switching it self off and then finding that I cannot switch it on again. I have found 2 solutions to this problem.

1) Plug the phone into the charger and then try switching it on, even though the phone had loads of charge this seemed to work.

2) More recently I held the on switch on, and nothing happened, then I touched where the home button would be, then tried switching it on again and it started up fine.