Long running query

Hello Experts,

The below query is taking 5-6 minutes on production. Every column in where clause is part of index(some are part of composite index).

SELECT

      T28.CONFLICT_ID,

      T28.LAST_UPD,

      T28.CREATED,

      T28.LAST_UPD_BY,

      T28.CREATED_BY,

      T28.MODIFICATION_NUM,

      T28.ROW_ID,

      T28.SR_AREA,

      T28.INS_PRODUCT

   FROM

       SIEBEL.S_USER T1,

       SIEBEL.S_ORG_EXT T2,

       SIEBEL.S_ORG_EXT_X T3,

       SIEBEL.S_CONTACT T4,

       SIEBEL.S_CONTACT T5,

       SIEBEL.S_ADDR_PER T6,

       SIEBEL.S_ASSET T7,

       SIEBEL.S_ORG_EXT T8,

       SIEBEL.S_ADDR_PER T9,

       SIEBEL.S_ASSET T10,