I am making a rollercoaster and attempting to add a button that makes a command block summon the Minecart onto the tracks and has the player automatically enter it.
I am using Minecraft Bedrock (specifically Windows 10) on 1.16.
When doing this you could use the possible commands:
/ride @a[tag=example] summon_ride minecart
/execute@e[tag=example] ~~~ tp @p @e[type=minecart]
(i'm not a full expert on the ride command but that command should solve your problem if this did not solve your problem please let me know) :)