This sounds a bit like the 1974 James Blish novel [All the Stars a Stage] and another site at: [Second review/summary]
Points that match:
I am desperately trying to find the title and author of a sci-fi book I read in the 1970s.
The story goes something like this...
Scientists on a planet discover, via the spectrum of their local star, that it is going to go supernova (or possibly red giant). A fleet of giant spacecraft is constructed and these escape to orbit, carrying some of the population with them.
When the sun explodes all life will end. No one will survive the blow-up; except the men and women who crowd into a few starships and fly away into space while there is still time,
One ship is damaged in rioting which breaks out on the planet but still makes it to orbit. he spacecraft leave the planet's orbit and escape the system. The damaged craft explodes. The people on the other ships then watch the end of their star.
We achieve blast off on page 80 of this 191 page book, Jorn and co leaving the screaming mobs behind to be burned to a cinder by solar radiation.
As time goes by the ships get further from each other as their wave front expands. Contact begins to be lost with craft one by one. On one ship the deduction is made that the ships are being picked off by encounters with predator civilisations as all the ships are heading towards the galactic centre where it is presumed the density of other civilizations will increase.
On page 111 Jorn and friends land on a planet, but are defeated by the native wildlife.
The ship is turned round and heads towards the outer rim of the galaxy. Finally the ship lands on the planet Earth before the rise of industrial civilisation on Earth.
Jorn is an elderly arthritic man, the ship lands on the ancient Earth, year 3900 B.C. In what I guess is an expression of religious faith on the part of Blish we are told that Jorn's people and the Earth people are built on the same "Model" and can interbreed. Alien genes enter the Earth gene pool, and alien myths based on Jorn's adventures enter Earth legend and religion.
In addition to the above you might remember something about the "familiars" which men and women have. A semi-parasitic creature that lives with each. There is a scene with them of some importance towards the end of the book.