Hotel Monterey (1972)
Hardline art-house movie (60mns, silent, no actors, no plot,no credits,static camera) filming customers in a budget New York hotel.
I watched it because this film was apparently a major influence on Kubrick when he made The Shining, and also greatly inspired many of David Lynch's films (especially Twin Peaks, Blue Velvet, Inland Empire) - and I can see why that could well be true.