  Using the Mandelstam-Tamm method we derive time-energy uncertainty relations
for neutrino oscillations. We demonstrate that the small energy uncertainty of
antineutrinos in a recently considered experiment with recoilless resonant
(M\"ossbauer) production and absorption of tritium antineutrinos is in conflict
with the energy uncertainty which, according to the time-energy uncertainty
relation, is necessary for neutrino oscillations to happen. A M\"ossbauer
neutrino experiment could provide a unique possibility to test the
applicability of the time-energy uncertainty relation to neutrino oscillations
and to reveal the true nature of neutrino oscillations.
