1989 535I (E36) Shuts Down

[wgf1960]

My 1989 535I shuts off and wont start when gets warm after about an hour of driving? If I let it cool for one hour it starts right back up.
Is it electrical ?

Any ideas ?
Thanks in advance
wgf1960 SJ CA

[wgf1960]

Shuts Down when warm.