Why does this circuit start at a very high value?
It's pretty simple. You forgot to set "UIC" in the .TRAN statement. Also, you need some kind of resistance at the joint node. (Not critical, but it removes some errors.) This is because you have an "all-frequency infinite impedance" (the current source) on one side and a "DC infinite impedance" on the other side. There's no galvanic path indicated to the node. So it helps to add one (namely, \$R_1\$.)



Here you can see the "uic" added to the .tran statement. Just click on that on your own schematic. This prevents LTspice from trying to find a default "operating point" before starting the simulation.

It's really no more complicated than that.