Random misfire on cylinders 1,3,AND5 WHAT CAN CAUSE IT on 1998 Cadillac Catera

after about 5 OR 10 MINS IT READS CODES 300,301,303,305 AND IT IDLES ROUGH

Asked by for the 1998 Cadillac Catera
These cars typically burn up the coils and ignition module, we have done several in the shop where I work. The valve covers leak oil and then these ignition components get oil soaked and fail.
This is a pricey repair, like $1800-2000, with the valve cover work, which must be done. The engine in your Caddy is a SAAB motor which is VERY high maintenance.
I was not aware that Caddys and Saabs share the same engine. Although, I do know that 3.0L Saab V-6 is a GM engine that Saab did minor adjustments to(at least that's what they told us at Saab FTP). Saab used a slightly thicker head gasket to lower the compression, added a turbo, altered the intake and exhaust manifolds, and added Direct Ignition with a "Trionic" ECU.
actually the Cadillac catera is an opal product not a saab, it is a rebadged opal omega.
1 more answer
could also be timming belt