I'm sweating blood to find any product or how-to to make time lapses with my Nikon P900. It seems to me, that my only option is to use the built-in time lapse modes, which sucks. I mean, it shoots in 2MP and the result is horrible. I've tried the interval mode as well, but the smallest interval is 30 seconds. I need simply a tool, to remotely shoot a picture like every 3 seconds and I gonna make a video after that from the separate images. The problem is I neither was able to find any shutter release compatible with P900 that can do this job. I've contacted a photographer shop and they also said that there is no compatible product for P900. Can you recommend me anything please?
What you're looking for is called an intervalometer. Unfortunately, nobody seems to have specifically made one that replaces Nikon's ML-L3 wireless shutter release (the remote that Nikon mentions on page 116 of the P900 Reference Manual).
This dpreview.com thread asks about your same problem — looking for an intervalometer for the P900. The only response links to a Gloxy Wireless Multi-exposure Intervalometer remote control for Nikon Coolpix P900 cameras. However, I don't believe it will actually work with the P900. I believe the mention of "P900" is linkbait. The pages states the remote replaces the Nikon MC-30, MC-DC2 and MC-DC1 remotes. These are all wired remotes. This indicates the remote probably includes a wireless receiver that has to plug into an appropriate connector on the camera, which the P900 lacks.
If you don't mind a bit of DIY, Limor Fried (Lady Ada) at Adafruit Industries has posted a fairly easy walkthrough of creating an intervalometer that emulates/replaces the ML-L3 using an Arduino kit, IR LED, and a couple other simple parts.