The Wkipedia article on tungsten says:
Naturally occurring tungsten consists of four stable isotopes ($^{182}\mathrm W$, $^{183}\mathrm W$, $^{184}\mathrm W$, and $^{186}\mathrm W$) and one very long-lived radioisotope, $^{180}\mathrm W$. Theoretically, all five can decay into isotopes of element $72$ (hafnium) by alpha emission, but only $^{180}\mathrm W$ has been observed to do so, with a half-life of $1.8 \pm 0.2 \times 10^{18}$ years; on average, this yields about two alpha decays of $^{180}\mathrm W$ per gram of natural tungsten per year. The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be at least $4 \times 10^{21}$ years.
So all isotopes of tungsten should, theoretically, release the occasional alpha particle but I can find no explanation of why.
But I can find nothing about elements 75 through 82 that says they should decay, slowly, via alpha decay....
So what is it about tungsten that makes theoretical scientists believe no isotope of tungsten should be completely stable? But only tungsten isotopes, not rhenium, osmium.... to lead?
(Important note: Experimentally, no one has seen this happen, except for $^{180}\mathrm W$)