what were some of the signs that Mt.Vesuvis from Pompeii was going to erupt?

Answer 1

The written accounts of Pliny the Younger tells us that Vesuvius showed very evident signs - not recognisable then. Earthquakes / tremors, large black columns of smoke belching from the volcano, very strong smell of sulphur.

Pliny the Yonger wrote to Tacitus about the death of his uncle, Pliny the Elder during the Eruption.
"Ash was falling onto the ships now, darker and denser the closer they went. Now it was bits of pumice, and rocks that were blackened and burned and shattered by the fire. Now the sea is shoal; debris from the mountain blocks the shore.

. . . the flames and smell of sulphur which gave warning of the approaching fire drove the others to take flight and roused him to stand up . . . then [he] suddenly collapsed, I imagine because the dense fumes choked his breathing by blocking his windpipe which was constitutionally weak and narrow and often inflamed . . . his body was found intact and uninjured, still fully clothed and looking more like sleep than death

Just no one had thought it was going to be a major eruption.