Bizeebmw

Find an Indy with Autologic Diagnostics. They can do it.

What model is it?

Diesels will smoke more on start up if the glow plugs are down. A very common fault code on BMW but very rarely causes a starting issue as on other makes. A fault code scan would tell you this,

Have you had an answer to this?

Have you tried the ignition switch? It's mounted behind the key barrel. Costs about £35 and take 30 mins to fit. Most common fault with e39 non start. If not get it in a diagnostic machine, only safe way to diagnose it without shovelling more money in.

Simple answer, get it diagnosed with good equipment. As stated, probably cam or crank sensors BUT you will save hours if you have a fault code!

Just be aware that the car should be recoded for towbar electrics. Otherwise your PDC (parking sensors) will go mental when in reverse and towing. Also because the car runs on a CAN bus system you may get a problem in the Light control module if you just chop the wires, also it can cause a problem with the climate. All of these I have seen after towbars fitted with no recoding. Just beware. If you have problems you don't have to go to BMW. Just find an Indy with Autologic.

Jack is right. A remap is the best option. There will be one near you and it's worth researching it to get the best option for you. Check out Celtic, I have done a few with good results.