IBM i SRC B90037FF

Indicates a CPF message was received during OS startup:

https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/rzahb/rzahbsrclist.htm#rzahbsrclist__letterb

Use the system control panel or HMC to retrieve the associated information to see the specific error information.  You can follow the problem analysis process to gather this information (I picked a Power8 system - usually best to pick documentation specific to your model, but for an OS startup issue like this that isn't as important):

https://www.ibm.com/support/knowledgecenter/POWER8/p8eal/p8eal_i5ospa.htm?pos=14

Post back after you have identified the specific error message if you need help resolving it.

Also helpful to understand if anything unusual happened before the IPL: PTFs installed, system ended abnormally, hardware maintenance, etc.

I eventually opened up a call ticket with IBM. I had to reinstall my OS... after I did that, I re-installed the latest PTFs and everything was back to normal. All the system values, libraries, user information was all as it was before the "corruption". The OS re-install only updated base OS files - not the user data I had on the system (which was minimal anyway)

Glad you were able to get it resolved.  

This one can be as simple as IPLing to DST and doing a little cleanup or some other service action, IPLing off the alternate micrcode, or drastic as a reinstall or recovery.  Really just depends on the underlying message behind the SRC.