EE 3.3.4 PHP Error

Hi all, I’m getting an error in EE 3.3.4 which I haven’t been able to figure out. I was hoping someone could give me a clue:

Warning Cannot modify header information - headers already sent by (output started at ee/legacy/core/Exceptions.php:115) ee/EllisLab/ExpressionEngine/Boot/boot.common.php, line 463 hide details

Severity: E_WARNING

Running php 7.0 SQL 5.0.12

Any feedback would be appreciated.