The charred remains of the woman, who has not been named, were discovered close to the town of Pianoro.
She was lying in woodland next to a petrol canister, around 200 metres from her car, police said in a statement.
Authorities made the discovery after locals reported the car, which had been in the valley for around two days.
The Swiss woman, married with two children, is thought to have bought the petrol canister on Monday morning, although it is unclear whether she committed suicide or was killed.
Police said she was a resident of Molinella, a village about 40 kilometres from where her body was found.