Constantly have to "soft reset" my phone

[BrandyWilliams]

Out of no where my phone screen just goes black.  I have only had my 4s for a month.  It hasnt been dropped and is always kept in the Otterbox Case I purchased with my phone.  I dont understand why I have to keep doing this.  atleast once per week, sometimes more I am soft resetting my phone.  Today was 3 times.  Has anybody had a problem like this?  Should I be taking my phone into a Verizon Store to have it looked at?

Thanks