Oracle database connection performance dropped to bottom, causing severe performance issues in web application and scheduler job failures

We have some batch scripts as task scheduler jobs, which are running good from few years. These jobs connects to DB and will do multiple inserts and update operations using sqlplus, sqlldr and java code (jar files). Suddenly we observed a very big performance issue across all these jobs. After monitoring some scripts for a long time, we identified that these jobs are waiting randomly from time to time and then continue running. There is no particular time frame for how long they wait or at which phase query execution they wait. Its completely random. A web Application is deployed in same machine, connects to same database. This application performance is also dropped from the same day. This is severely hindering business activities. I really appreciate any advise\suggestions that can help us resolve this issue. Oracle DB: 18c We tried below activities. 1. Validated windows app server and didn't found any new installations\updates\patches. 2. Coordinated with network team and found no traffic issues are identified on both app and DB servers. 3. No heavy load packets are on DB DNS 4. DB is running normal. It is a shared instance and no other application\team found any issues in performance. Some how i feels like some other process is holding our web application and task schedule connection processes. I am banging my brains to bring this connection performance to normal situation. Any advise is highly appreciated.