Not necessarily spontaneous, but any type of spiritually assisted healing.
If so, can you elaborate?
If not, can you offer a reference?
Buddhism Stack Exchange is a question and answer site for people practicing or interested in Buddhist philosophy, teaching, and practice. It only takes a minute to sign up.Sign up to join this community
There are several cases of working cures mentioned in the suttas many more in the Jataka stories which are much later. Two oustanding cases found in the suttas are the one where Angulimala http://obo.genaud.net/backmatter/appendixes/personalities/angulimala.htm did an act of truth to relieve a woman of a painful labor, another is the case of the Buddha himself 'bending down his mind' to the suppression of an illness. http://obo.genaud.net/dhamma-vinaya/bs/dn.16.rhyt.bs_1.2.htm scroll down to #28
The 'act of truth' is a declaration made to the gods of the truth of some statement in the form of a wish: "If such and such is the truth, let such and such happen." Usually the thing being declared to be the truth must be something hard to believe or embarassing, something not likely to be revealed unless under strong motivation to do so.
Generally the Buddha suggests not working cures with the idea that beings have their kamma to live out. Working a cure does not relieve a person of the experience of his bad kamma, it just postpones it and that may not be a wise idea if it postpones the experience beyond its manifestation in this life there is the possibility that the next life will be so hazardous (as in animal life) that insight and taking counter-measures would be highly unlikely. Consequently curing someone may not be doing them any favor.
There is the tradition of the Medicine Buddha in Mahayana Buddhism - I'm most familiar with his appearance in the Lotus Sutra but he has an influence further that that one (albeit very influential) sutra. The Medicine Buddha is associated with mental and physical healing. While this Buddha certainly does heal the existential suffering that is the more familiar concern of Buddhism he does also heal physical aliments as well in some traditions. To quote from wiki
[The Medicine Buddha has] very powerful method for healing and increasing healing powers both for oneself and others, but also for overcoming the inner sickness of attachment, hatred, and ignorance, thus to meditate on the Medicine Buddha can help decrease physical and mental illness and suffering
As a further aside I was watching a documentary about the Dalai Lama and he was receiving people for blessings. One man brought him a young child with a nasty looking open fracture to ask for the Dalai Lama's healing. So a belief in healing through blessing clearly exists in the Buddhist world today. I have to say that the Dalai Lama was having none of it. He strongly suggested that the child should be taken to hospital as soon as possible.
Reference Note: I'm fairly certain that the above scene comes from the documentary The Unwinking Gaze but I'm very happy to be corrected on that point if anyone knows better.