High pressure contol

Question

I have come home a couple of time and my A/C unit is on and running but blowing hot air. I went outside to check the compressor and the fan on that unit was not spinning. I saw a switch on the bottom of the unit that said High pressure control push to reset, I did that and the unit started running again and cooling but it has happen twice in the last week is there some major going wrong with this unit? it is only 5yr old.