What are the probable causes of joint pain at multiple joints at the same time?

Very little information here.

Uhh. Could be infection. A good case of the flu, can start with achy joints.

Inactivity. Laying around can mess up your joints.

There are conditions. Like DJD. Degenerative Joint Disease.

Arthritis.

Rheumatoid arthritis.

General “wear and tear.”

Loss of lubricant. (Glucosamine, and condroiten can help.)

Lyme disease is another. Allergic reactions too

Lupus

In osteo arthritis pain is not necessarily symmetrical but in RA joint pain will generally be on both sides of the body.