Infraspace

Infraspace is a region in the IDW comics portion of the Generation 1 continuity family

Not much is known of infraspace. A Transformer can seemingly exist there without a body, or perhaps it is where Transformers whose bodies have been destroyed go.

IDW Comics continuity
Optimus Prime had received a severe beat-down from an Ore-13-powered Megatron, and was on the verge of terminal shutdown. In a desperate ploy, he transferred his higher functions into his trailer section, giving the appearance of lifelessness.

During the transfer, Prime's consciousness drifted through infraspace. While there, he felt a sinister presence that seemed to recognize and watch him.

What connection infraspace may have to the Dead Universe has yet to be revealed.